diff --git a/framework/base/Component.php b/framework/base/Component.php
index 5d96cb6..1705904 100644
--- a/framework/base/Component.php
+++ b/framework/base/Component.php
@@ -29,12 +29,12 @@ namespace yii\base;
  * Event names are case-insensitive.
  *
  * An event can be attached with one or multiple PHP callbacks, called *event handlers*.
- * One can call [[raiseEvent]] to raise an event. When an event is raised, the attached
+ * One can call [[raiseEvent()]] to raise an event. When an event is raised, the attached
  * event handlers will be invoked automatically in the order they are attached to the event.
  *
  * To attach an event handler to an event, call [[attachEventHandler]]. Alternatively,
  * you can use the assignment syntax: `$component->onClick = $callback;`,
- * where `$callback` refers to a valid PHP callback, which can be one of the followings:
+ * where `$callback` refers to a valid PHP callback which can be one of the followings:
  *
  * - global function: `'handleOnClick'`
  * - object method: `array($object, 'handleOnClick')`
@@ -59,21 +59,25 @@ namespace yii\base;
  * ~~~
  *
  *
- * A behavior is an instance of [[Behavior]] or its child class. When a behavior is
- * attached to a component, its public properties and methods can be accessed via the
- * component directly, as if the component owns those properties and methods.
+ * A behavior is an instance of [[Behavior]] or its child class. A component can be attached
+ * with one or multiple behaviors. When a behavior is attached to a component, its public
+ * properties and methods can be accessed via the component directly, as if the component owns
+ * those properties and methods.
  *
- * Multiple behaviors can be attached to the same component.
- *
- * To attach a behavior to a component, call [[attachBehavior]]; to detach a behavior
- * from the component, call [[detachBehavior]].
+ * To attach a behavior to a component, declare it in [[behaviors()]], or explicitly call [[attachBehavior]].
  *
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
 class Component extends Object
 {
+	/**
+	 * @var Vector[] the attached event handlers (event name => handlers)
+	 */
 	private $_e;
+	/**
+	 * @var Behavior[] the attached behaviors (behavior name => behavior)
+	 */
 	private $_b;
 
 	/**
@@ -104,12 +108,11 @@ class Component extends Object
 				$this->_e[$name] = new Vector;
 			}
 			return $this->_e[$name];
-		} elseif (isset($this->_b[$name])) { // behavior
-			return $this->_b[$name];
-		} elseif (is_array($this->_b)) { // a behavior property
-			foreach ($this->_b as $object) {
-				if ($object->canGetProperty($name)) {
-					return $object->$name;
+		} else { // behavior property
+			$this->ensureBehaviors();
+			foreach ($this->_b as $behavior) {
+				if ($behavior->canGetProperty($name)) {
+					return $behavior->$name;
 				}
 			}
 		}
@@ -143,10 +146,11 @@ class Component extends Object
 				$this->_e[$name] = new Vector;
 			}
 			return $this->_e[$name]->add($value);
-		} elseif (is_array($this->_b)) { // behavior
-			foreach ($this->_b as $object) {
-				if ($object->canSetProperty($name)) {
-					return $object->$name = $value;
+		} else { // behavior property
+			$this->ensureBehaviors();
+			foreach ($this->_b as $behavior) {
+				if ($behavior->canSetProperty($name)) {
+					return $behavior->$name = $value;
 				}
 			}
 		}
@@ -178,12 +182,11 @@ class Component extends Object
 		} elseif (method_exists($this, $name) && strncasecmp($name, 'on', 2) === 0) { // has event handler
 			$name = strtolower($name);
 			return isset($this->_e[$name]) && $this->_e[$name]->getCount();
-		} elseif (isset($this->_b[$name])) { // has behavior
-			return true;
-		} elseif (is_array($this->_b)) {
-			foreach ($this->_b as $object) {
-				if ($object->canGetProperty($name)) {
-					return $object->$name !== null;
+		} else { // behavior property
+			$this->ensureBehaviors();
+			foreach ($this->_b as $behavior) {
+				if ($behavior->canGetProperty($name)) {
+					return $behavior->$name !== null;
 				}
 			}
 		}
@@ -207,16 +210,17 @@ class Component extends Object
 	{
 		$setter = 'set' . $name;
 		if (method_exists($this, $setter)) { // write property
-			return $this->$setter(null);
+			$this->$setter(null);
+			return;
 		} elseif (method_exists($this, $name) && strncasecmp($name, 'on', 2) === 0) { // event
 			unset($this->_e[strtolower($name)]);
 			return;
-		} elseif (isset($this->_b[$name])) { // behavior
-			return $this->detachBehavior($name);
-		} elseif (is_array($this->_b)) { // behavior property
-			foreach ($this->_b as $object) {
-				if ($object->canSetProperty($name)) {
-					return $object->$name = null;
+		} else { // behavior property
+			$this->ensureBehaviors();
+			foreach ($this->_b as $behavior) {
+				if ($behavior->canSetProperty($name)) {
+					$behavior->$name = null;
+					return;
 				}
 			}
 		}
@@ -247,14 +251,42 @@ class Component extends Object
 			}
 		}
 
-		if ($this->_b !== null) {
-			foreach ($this->_b as $object) {
-				if (method_exists($object, $name)) {
-					return call_user_func_array(array($object, $name), $params);
-				}
+		$this->ensureBehaviors();
+		foreach ($this->_b as $object) {
+			if (method_exists($object, $name)) {
+				return call_user_func_array(array($object, $name), $params);
 			}
 		}
-		throw new Exception('Unknown method: ' . get_class($this) . "::$name()");
+
+		throw new Exception('Calling unknown method: ' . get_class($this) . "::$name()");
+	}
+
+	/**
+	 * Returns a list of behaviors that this component should behave as.
+	 *
+	 * Child classes may override this method to specify the behaviors they want to behave as.
+	 *
+	 * The return value of this method should be an array of behavior objects or configurations
+	 * indexed by behavior names. A behavior configuration can be either a string specifying
+	 * the behavior class or an array of the following structure:
+	 *
+	 * ~~~
+	 * 'behaviorName' => array(
+	 *	 'class' => 'BehaviorClass',
+	 *	 'property1' => 'value1',
+	 *	 'property2' => 'value2',
+	 * )
+	 * ~~~
+	 *
+	 * Note that a behavior class must extend from [[Behavior]].
+	 *
+	 * Behaviors declared in this method will be attached to the component on demand.
+	 *
+	 * @return array the behavior configurations.
+	 */
+	public function behaviors()
+	{
+		return array();
 	}
 
 	/**
@@ -270,12 +302,13 @@ class Component extends Object
 	}
 
 	/**
-	 * Returns a value indicating whether there is any handler attached to the event.
+	 * Returns a value indicating whether there is any handler attached to the named event.
 	 * @param string $name the event name
 	 * @return boolean whether there is any handler attached to the event.
 	 */
 	public function hasEventHandlers($name)
 	{
+		$this->ensureBehaviors();
 		$name = strtolower($name);
 		return isset($this->_e[$name]) && $this->_e[$name]->getCount();
 	}
@@ -365,6 +398,7 @@ class Component extends Object
 	 */
 	public function raiseEvent($name, $event)
 	{
+		$this->ensureBehaviors();
 		$name = strtolower($name);
 		if ($event instanceof Event) {
 			$event->name = $name;
@@ -406,6 +440,7 @@ class Component extends Object
 	 */
 	public function asa($behavior)
 	{
+		$this->ensureBehaviors();
 		return isset($this->_b[$behavior]) ? $this->_b[$behavior] : null;
 	}
 
@@ -415,11 +450,11 @@ class Component extends Object
 	 * configuration. After that, the behavior object will be attached to
 	 * this component by calling the [[Behavior::attach]] method.
 	 * @param string $name the behavior's name. It should uniquely identify this behavior.
-	 * @param mixed $behavior the behavior configuration. This can be one of the following:
+	 * @param string|array|Behavior $behavior the behavior configuration. This can be one of the following:
 	 *
 	 *  - a [[Behavior]] object
 	 *  - a string specifying the behavior class
-	 *  - an object configuration array that will be passed to [[\Yii::createObject]] to create the behavior object.
+	 *  - an object configuration array that will be passed to [[\Yii::createObject()]] to create the behavior object.
 	 *
 	 * @return Behavior the behavior object
 	 * @see detachBehavior
@@ -457,10 +492,12 @@ class Component extends Object
 	public function detachBehavior($name)
 	{
 		if (isset($this->_b[$name])) {
-			$this->_b[$name]->detach($this);
 			$behavior = $this->_b[$name];
 			unset($this->_b[$name]);
+			$behavior->detach($this);
 			return $behavior;
+		} else {
+			return null;
 		}
 	}
 
@@ -470,10 +507,24 @@ class Component extends Object
 	public function detachBehaviors()
 	{
 		if ($this->_b !== null) {
-			foreach ($this->_b as $name => $behavior) {
+			$behaviors = $this->_b;
+			$this->_b = null;
+			foreach ($behaviors as $name => $behavior) {
 				$this->detachBehavior($name);
 			}
-			$this->_b = null;
+		}
+	}
+
+	/**
+	 * Makes sure that the behaviors declared in [[behaviors()]] are attached to this component.
+	 */
+	public function ensureBehaviors()
+	{
+		if ($this->_b === null) {
+			$this->_b = array();
+			foreach ($this->behaviors() as $name => $behavior) {
+				$this->attachBehavior($name, $behavior);
+			}
 		}
 	}
 }
diff --git a/framework/base/Model.php b/framework/base/Model.php
index 3f04685..bceea5a 100644
--- a/framework/base/Model.php
+++ b/framework/base/Model.php
@@ -9,6 +9,8 @@
 
 namespace yii\base;
 
+use yii\util\Text;
+
 /**
  * Model is the base class for data models.
  *
@@ -22,7 +24,6 @@ namespace yii\base;
  *
  * Model also provides a set of events for further customization:
  *
- * - [[onAfterInit]]: an event raised at the end of [[init()]]
  * - [[onBeforeValidate]]: an event raised at the beginning of [[validate()]]
  * - [[onAfterValidate]]: an event raised at the end of [[validate()]]
  *
@@ -32,7 +33,7 @@ namespace yii\base;
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
-class Model extends Component implements Initable, \IteratorAggregate, \ArrayAccess
+class Model extends Component implements \IteratorAggregate, \ArrayAccess
 {
 	private static $_attributes = array(); // class name => array of attribute names
 	private $_errors; // attribute name => array of errors
@@ -49,50 +50,9 @@ class Model extends Component implements Initable, \IteratorAggregate, \ArrayAcc
 	}
 
 	/**
-	 * Initializes this model.
-	 *
-	 * This method is required by the [[Initable]] interface. It is invoked by [[\Yii::createObject]]
-	 * after it creates the new model instance and initializes the model properties.
-	 *
-	 * The default implementation calls [[behaviors]] and registers any available behaviors.
-	 * You may override this method with additional initialization logic (e.g. establish DB connection).
-	 * Make sure you call the parent implementation.
-	 */
-	public function init()
-	{
-		$this->attachBehaviors($this->behaviors());
-		$this->afterInit();
-	}
-
-	/**
-	 * Returns a list of behaviors that this model should behave as.
-	 * The return value should be an array of behavior configurations indexed by
-	 * behavior names. Each behavior configuration can be either a string specifying
-	 * the behavior class or an array of the following structure:
-	 *
-	 * ~~~
-	 * 'behaviorName' => array(
-	 *	 'class' => 'BehaviorClass',
-	 *	 'property1' => 'value1',
-	 *	 'property2' => 'value2',
-	 * )
-	 * ~~~
-	 *
-	 * Note that a behavior class must extend from [[Behavior]]. Behaviors declared
-	 * in this method will be attached to the model when [[init]] is invoked.
-	 *
-	 * @return array the behavior configurations.
-	 * @see init
-	 */
-	public function behaviors()
-	{
-		return array();
-	}
-
-	/**
 	 * Returns the list of attribute names.
 	 * By default, this method returns all public non-static properties of the class.
-	 * You may override this method to change the default.
+	 * You may override this method to change the default behavior.
 	 * @return array list of attribute names.
 	 */
 	public function attributeNames()
@@ -116,7 +76,7 @@ class Model extends Component implements Initable, \IteratorAggregate, \ArrayAcc
 	/**
 	 * Returns the validation rules for attributes.
 	 *
-	 * Validation rules are used by [[validate]] to check if attribute values are valid.
+	 * Validation rules are used by [[validate()]] to check if attribute values are valid.
 	 * Child classes may override this method to declare different validation rules.
 	 *
 	 * Each rule is an array with the following structure:
@@ -140,26 +100,31 @@ class Model extends Component implements Initable, \IteratorAggregate, \ArrayAcc
 	 *  - additional name-value pairs can be specified to initialize the corresponding validator properties.
 	 *	Please refer to individual validator class API for possible properties.
 	 *
-	 * A validator can be either a model class method or an object.
-	 * If the former, the method must have the following signature:
+	 * A validator can be either an object of a class extending [[\yii\validators\Validator]],
+	 * or a model class method (called *inline validator*) that has the following signature:
 	 *
 	 * ~~~
 	 * // $params refers to validation parameters given in the rule
 	 * function validatorName($attribute, $params)
 	 * ~~~
 	 *
-	 * If the latter, the object must be extending from [[\yii\validators\Validator]].
-	 * Yii provides a set of [[\yii\validators\Validator::builtInValidators|built-in validators]].
-	 * They each have an alias name which can be used when specifying a validation rule.
+	 * Yii also provides a set of [[\yii\validators\Validator::builtInValidators|built-in validators]].
+	 * They each has an alias name which can be used when specifying a validation rule.
 	 *
-	 * The following are some examples:
+	 * Below are some examples:
 	 *
 	 * ~~~
 	 * array(
+	 *   // built-in "required" validator
 	 *	 array('username', 'required'),
+	 *   // built-in "length" validator customized with "min" and "max" properties
 	 *	 array('username', 'length', 'min'=>3, 'max'=>12),
+	 *   // built-in "compare" validator that is used in "register" scenario only
 	 *	 array('password', 'compare', 'compareAttribute'=>'password2', 'on'=>'register'),
+	 *   // an inline validator defined via the "authenticate()" method in the model class
 	 *	 array('password', 'authenticate', 'on'=>'login'),
+	 *   // a validator of class "CaptchaValidator"
+	 *   array('captcha', 'CaptchaValidator'),
 	 * );
 	 * ~~~
 	 *
@@ -180,7 +145,7 @@ class Model extends Component implements Initable, \IteratorAggregate, \ArrayAcc
 	 * `firstName`, we can declare a label `First Name` which is more user-friendly and can
 	 * be displayed to end users.
 	 *
-	 * By default an attribute label is generated using [[generateAttributeLabel]].
+	 * By default an attribute label is generated using [[generateAttributeLabel()]].
 	 * This method allows you to explicitly specify attribute labels.
 	 *
 	 * Note, in order to inherit labels defined in the parent class, a child class needs to
@@ -197,21 +162,21 @@ class Model extends Component implements Initable, \IteratorAggregate, \ArrayAcc
 	/**
 	 * Performs the data validation.
 	 *
-	 * This method executes the validation rules as declared in [[rules]].
+	 * This method executes the validation rules as declared in [[rules()]].
 	 * Only the rules applicable to the current [[scenario]] will be executed.
 	 * A rule is considered applicable to a scenario if its `on` option is not set
 	 * or contains the scenario.
 	 *
-	 * This method will call [[beforeValidate]] and [[afterValidate]] before and
-	 * after actual validation, respectively. If [[beforeValidate]] returns false,
-	 * the validation and [[afterValidate]] will be cancelled.
+	 * This method will call [[beforeValidate()]] and [[afterValidate()]] before and
+	 * after actual validation, respectively. If [[beforeValidate()]] returns false,
+	 * the validation and [[afterValidate()]] will be cancelled.
 	 *
-	 * Errors found during the validation can be retrieved via [[getErrors]].
+	 * Errors found during the validation can be retrieved via [[getErrors()]].
 	 *
 	 * @param array $attributes list of attributes that should be validated.
 	 * If this parameter is empty, it means any attribute listed in the applicable
 	 * validation rules should be validated.
-	 * @param boolean $clearErrors whether to call [[clearErrors]] before performing validation
+	 * @param boolean $clearErrors whether to call [[clearErrors()]] before performing validation
 	 * @return boolean whether the validation is successful without any error.
 	 * @see beforeValidate
 	 * @see afterValidate
@@ -232,19 +197,6 @@ class Model extends Component implements Initable, \IteratorAggregate, \ArrayAcc
 	}
 
 	/**
-	 * This method is invoked at the end of [[init()]].
-	 * The default implementation raises the [[onAfterInit]] event.
-	 * You may override this method to do postprocessing after model creation.
-	 * Make sure you call the parent implementation so that the event is raised properly.
-	 */
-	public function afterInit()
-	{
-		if ($this->hasEventHandlers('onAfterInit')) {
-			$this->onAfterInit(new Event($this));
-		}
-	}
-
-	/**
 	 * This method is invoked before validation starts.
 	 * The default implementation raises the [[onBeforeValidate]] event.
 	 * You may override this method to do preliminary checks before validation.
@@ -276,24 +228,6 @@ class Model extends Component implements Initable, \IteratorAggregate, \ArrayAcc
 	}
 
 	/**
-	 * This event is raised by [[init]] when initializing the model.
-	 * @param Event $event the event parameter
-	 */
-	public function onInit($event)
-	{
-		$this->raiseEvent(__FUNCTION__, $event);
-	}
-
-	/**
-	 * This event is raised at the end of [[init()]].
-	 * @param Event $event the event parameter
-	 */
-	public function onAfterInit($event)
-	{
-		$this->raiseEvent(__FUNCTION__, $event);
-	}
-
-	/**
 	 * This event is raised before the validation is performed.
 	 * @param ValidationEvent $event the event parameter
 	 */
@@ -312,9 +246,9 @@ class Model extends Component implements Initable, \IteratorAggregate, \ArrayAcc
 	}
 
 	/**
-	 * Returns all the validators declared in [[rules]].
+	 * Returns all the validators declared in [[rules()]].
 	 *
-	 * This method differs from [[getActiveValidators]] in that the latter
+	 * This method differs from [[getActiveValidators()]] in that the latter
 	 * only returns the validators applicable to the current [[scenario]].
 	 *
 	 * Because this method returns a [[Vector]] object, you may
@@ -339,7 +273,7 @@ class Model extends Component implements Initable, \IteratorAggregate, \ArrayAcc
 	 * Returns the validators applicable to the current [[scenario]].
 	 * @param string $attribute the name of the attribute whose applicable validators should be returned.
 	 * If this is null, the validators for ALL attributes in the model will be returned.
-	 * @return array the validators applicable to the current [[scenario]].
+	 * @return \yii\validators\Validator[] the validators applicable to the current [[scenario]].
 	 */
 	public function getActiveValidators($attribute = null)
 	{
@@ -356,8 +290,8 @@ class Model extends Component implements Initable, \IteratorAggregate, \ArrayAcc
 	}
 
 	/**
-	 * Creates validator objects based on the validation rules specified in [[rules]].
-	 * Unlike [[getValidators]], calling this method each time, it will return a new list of validators.
+	 * Creates validator objects based on the validation rules specified in [[rules()]].
+	 * Unlike [[getValidators()]], each time this method is called, a new list of validators will be returned.
 	 * @return Vector validators
 	 */
 	public function createValidators()
@@ -399,7 +333,7 @@ class Model extends Component implements Initable, \IteratorAggregate, \ArrayAcc
 	 */
 	public function isAttributeSafe($attribute)
 	{
-		$validators = $this->getActiveValidators();
+		$validators = $this->getActiveValidators($attribute);
 		foreach ($validators as $validator) {
 			if (!$validator->safe) {
 				return false;
@@ -523,13 +457,13 @@ class Model extends Component implements Initable, \IteratorAggregate, \ArrayAcc
 	 */
 	public function generateAttributeLabel($name)
 	{
-		return ucwords(trim(strtolower(str_replace(array('-', '_', '.'), ' ', preg_replace('/(?<![A-Z])[A-Z]/', ' \0', $name)))));
+		return Text::name2words($name, true);
 	}
 
 	/**
 	 * Returns attribute values.
 	 * @param array $names list of attributes whose value needs to be returned.
-	 * Defaults to null, meaning all attributes listed in [[attributeNames]] will be returned.
+	 * Defaults to null, meaning all attributes listed in [[attributeNames()]] will be returned.
 	 * If it is an array, only the attributes in the array will be returned.
 	 * @return array attribute values (name=>value).
 	 */
diff --git a/framework/db/ar/ActiveMetaData.php b/framework/db/ar/ActiveMetaData.php
new file mode 100644
index 0000000..edd2baa
--- /dev/null
+++ b/framework/db/ar/ActiveMetaData.php
@@ -0,0 +1,76 @@
+<?php
+
+namespace yii\db\ar;
+
+use yii\db\Exception;
+
+/**
+ * ActiveMetaData represents the meta-data for an Active Record class.
+ *
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class ActiveMetaData
+{
+	/**
+	 * @var TableSchema the table schema information
+	 */
+	public $table;
+	/**
+	 * @var array list of relations
+	 */
+	public $relations = array();
+
+	/**
+	 * Constructor.
+	 * @param string $modelClass the model class name
+	 */
+	public function __construct($modelClass)
+	{
+		$tableName = $modelClass::tableName();
+		$table = $modelClass::getDbConnection()->getDriver()->getTableSchema($tableName);
+		if ($table === null) {
+			throw new Exception("Unable to find table '$tableName' for ActiveRecord class '$modelClass'.");
+		}
+		if ($table->primaryKey === null) {
+			$primaryKey = $modelClass::primaryKey();
+			if ($primaryKey !== null) {
+				$table->fixPrimaryKey($primaryKey);
+			} else {
+				throw new Exception("The table '$tableName' for ActiveRecord class '$modelClass' does not have a primary key.");
+			}
+		}
+		$this->table = $table;
+
+		foreach ($modelClass::relations() as $name => $config) {
+			$this->addRelation($name, $config);
+		}
+	}
+
+	/**
+	 * Adds a relation.
+	 *
+	 * $config is an array with three elements:
+	 * relation type, the related active record class and the foreign key.
+	 *
+	 * @throws Exception
+	 * @param string $name $name Name of the relation.
+	 * @param array $config $config Relation parameters.
+	 * @return void
+	 */
+	public function addRelation($name, $config)
+	{
+		if (preg_match('/^(\w+)\s*:\s*\\\\?([\w\\\\]+)(\[\])?$/', $name, $matches)) {
+			if (is_string($config)) {
+				$config = array('on' => $config);
+			}
+			$relation = ActiveRelation::newInstance($config);
+			$relation->name = $matches[1];
+			$relation->modelClass = '\\' . $matches[2];
+			$relation->hasMany = isset($matches[3]);
+			$this->relations[$relation->name] = $relation;
+		} else {
+			throw new Exception("Relation name in bad format: $name");
+		}
+	}
+}
\ No newline at end of file
diff --git a/framework/db/ar/ActiveQuery.php b/framework/db/ar/ActiveQuery.php
new file mode 100644
index 0000000..8d7caca
--- /dev/null
+++ b/framework/db/ar/ActiveQuery.php
@@ -0,0 +1,233 @@
+<?php
+/**
+ * ActiveQuery class file.
+ *
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright &copy; 2008-2012 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\db\ar;
+
+/**
+ * ActiveFinder.php is ...
+ * todo: add SQL monitor
+ *
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class ActiveQuery extends \yii\db\dao\BaseQuery implements \IteratorAggregate, \ArrayAccess, \Countable
+{
+	public $modelClass;
+
+	public $with;
+	public $alias;
+	public $index;
+
+	private $_count;
+	private $_sql;
+	private $_countSql;
+	private $_asArray;
+	private $_records;
+
+	public function all()
+	{
+		return $this->performQuery();
+	}
+
+	public function one()
+	{
+		$this->limit = 1;
+		$records = $this->performQuery();
+		if (isset($records[0])) {
+			$this->_count = 1;
+			return $records[0];
+		} else {
+			$this->_count = 0;
+			return null;
+		}
+	}
+
+	public function asArray($value = true)
+	{
+		$this->_asArray = $value;
+	}
+
+	protected function performQuery()
+	{
+		$class = $this->modelClass;
+		$db = $class::getDbConnection();
+		$this->_sql = $this->getSql($db);
+		$command = $db->createCommand($this->_sql);
+		$command->bindValues($this->params);
+		$rows = $command->queryAll();
+		if ($this->_asArray) {
+			$records = $rows;
+		} else {
+			$records = array();
+			foreach ($rows as $row) {
+				$records[] = $class::populateRecord($row);
+			}
+		}
+		$this->_count = count($records);
+		return $records;
+	}
+
+	public function with()
+	{
+
+	}
+//
+//	public function getSql($connection = null)
+//	{
+//
+//	}
+
+	public function setSql($value)
+	{
+		$this->_sql = $value;
+	}
+
+	public function getCountSql()
+	{
+
+	}
+
+	public function getOneSql()
+	{
+
+	}
+
+	/**
+	 * Returns the number of items in the vector.
+	 * @return integer the number of items in the vector
+	 */
+	public function getCount()
+	{
+		if ($this->_count !== null) {
+			return $this->_count;
+		} else {
+			return $this->_count = $this->performCountQuery();
+		}
+	}
+
+	protected function performCountQuery()
+	{
+		$select = $this->select;
+		$this->select = 'COUNT(*)';
+		$class = $this->modelClass;
+		$command = $this->createCommand($class::getDbConnection());
+		$this->_countSql = $command->getSql();
+		$count = $command->queryScalar();
+		$this->select = $select;
+		return $count;
+	}
+
+	/**
+	 * Sets the parameters about query caching.
+	 * This is a shortcut method to {@link CDbConnection::cache()}.
+	 * It changes the query caching parameter of the {@link dbConnection} instance.
+	 * @param integer $duration the number of seconds that query results may remain valid in cache.
+	 * If this is 0, the caching will be disabled.
+	 * @param CCacheDependency $dependency the dependency that will be used when saving the query results into cache.
+	 * @param integer $queryCount number of SQL queries that need to be cached after calling this method. Defaults to 1,
+	 * meaning that the next SQL query will be cached.
+	 * @return ActiveRecord the active record instance itself.
+	 */
+	public function cache($duration, $dependency = null, $queryCount = 1)
+	{
+		$this->connection->cache($duration, $dependency, $queryCount);
+		return $this;
+	}
+
+	/**
+	 * Returns an iterator for traversing the items in the vector.
+	 * This method is required by the SPL interface `IteratorAggregate`.
+	 * It will be implicitly called when you use `foreach` to traverse the vector.
+	 * @return Iterator an iterator for traversing the items in the vector.
+	 */
+	public function getIterator()
+	{
+		$records = $this->performQuery();
+		return new \yii\base\VectorIterator($records);
+	}
+
+	/**
+	 * Returns the number of items in the vector.
+	 * This method is required by the SPL `Countable` interface.
+	 * It will be implicitly called when you use `count($vector)`.
+	 * @return integer number of items in the vector.
+	 */
+	public function count()
+	{
+		return $this->getCount();
+	}
+
+	/**
+	 * Returns a value indicating whether there is an item at the specified offset.
+	 * This method is required by the SPL interface `ArrayAccess`.
+	 * It is implicitly called when you use something like `isset($vector[$offset])`.
+	 * @param integer $offset the offset to be checked
+	 * @return boolean whether there is an item at the specified offset.
+	 */
+	public function offsetExists($offset)
+	{
+		if ($this->_records === null) {
+			$this->_records = $this->performQuery();
+		}
+		return isset($this->_records[$offset]);
+	}
+
+	/**
+	 * Returns the item at the specified offset.
+	 * This method is required by the SPL interface `ArrayAccess`.
+	 * It is implicitly called when you use something like `$value = $vector[$offset];`.
+	 * This is equivalent to [[itemAt]].
+	 * @param integer $offset the offset to retrieve item.
+	 * @return mixed the item at the offset
+	 * @throws Exception if the offset is out of range
+	 */
+	public function offsetGet($offset)
+	{
+		if ($this->_records === null) {
+			$this->_records = $this->performQuery();
+		}
+		return isset($this->_records[$offset]) ? $this->_records[$offset] : null;
+	}
+
+	/**
+	 * Sets the item at the specified offset.
+	 * This method is required by the SPL interface `ArrayAccess`.
+	 * It is implicitly called when you use something like `$vector[$offset] = $item;`.
+	 * If the offset is null or equal to the number of the existing items,
+	 * the new item will be appended to the vector.
+	 * Otherwise, the existing item at the offset will be replaced with the new item.
+	 * @param integer $offset the offset to set item
+	 * @param mixed $item the item value
+	 * @throws Exception if the offset is out of range, or the vector is read only.
+	 */
+	public function offsetSet($offset, $item)
+	{
+		if ($this->_records === null) {
+			$this->_records = $this->performQuery();
+		}
+		$this->_records[$offset] = $item;
+	}
+
+	/**
+	 * Unsets the item at the specified offset.
+	 * This method is required by the SPL interface `ArrayAccess`.
+	 * It is implicitly called when you use something like `unset($vector[$offset])`.
+	 * This is equivalent to [[removeAt]].
+	 * @param integer $offset the offset to unset item
+	 * @throws Exception if the offset is out of range, or the vector is read only.
+	 */
+	public function offsetUnset($offset)
+	{
+		if ($this->_records === null) {
+			$this->_records = $this->performQuery();
+		}
+		unset($this->_records[$offset]);
+	}
+}
diff --git a/framework/db/ar/ActiveRecord.php b/framework/db/ar/ActiveRecord.php
index 331dd09..29ca6a7 100644
--- a/framework/db/ar/ActiveRecord.php
+++ b/framework/db/ar/ActiveRecord.php
@@ -51,26 +51,40 @@ abstract class ActiveRecord extends \yii\base\Model
 		}
 	}
 
-	public static function find($query = null)
-	{
-		$finder = static::createFinder();
-		if ($query instanceof Query) {
-			$finder->query = $query;
-		} elseif ($query !== null) {
-			// todo: findByPk
+	/**
+	 * @static
+	 * @param string|array|ActiveQuery $q
+	 * @return ActiveQuery
+	 * @throws \yii\db\Exception
+	 */
+	public static function find($q = null)
+	{
+		$query = $q instanceof ActiveQuery? $q : static::createQuery();
+		$query->modelClass = '\\' . get_called_class();
+		$query->from = static::tableName();
+		if (is_array($q)) {
+			$query->where($q);
+		} elseif ($q !== null && $query !== $q) {
+			$primaryKey = static::getMetaData()->table->primaryKey;
+			if (is_string($primaryKey)) {
+				$query->where(array($primaryKey => $q));
+			} else {
+				throw new Exception("Multiple column values are required to find by composite primary keys.");
+			}
 		}
-		return $finder;
+		return $query;
 	}
 
 	public static function findBySql($sql, $params = array())
 	{
-		$finder = static::createFinder();
+		$query = static::createQuery();
 		if (!is_array($params)) {
 			$params = func_get_args();
 			array_shift($params);
 		}
-		$finder->setSql($sql);
-		return $finder->params($params);
+		$query->setSql($sql);
+		$query->modelClass = '\\' . get_called_class();
+		return $query->params($params);
 	}
 
 	public static function exists($condition, $params)
@@ -93,9 +107,9 @@ abstract class ActiveRecord extends \yii\base\Model
 
 	}
 
-	public static function createFinder()
+	public static function createQuery()
 	{
-		return new ActiveFinder('\\' . get_called_class());
+		return new ActiveQuery('\\' . get_called_class());
 	}
 
 	/**
@@ -149,6 +163,26 @@ abstract class ActiveRecord extends \yii\base\Model
 	}
 
 	/**
+	 * Declares the relations for this ActiveRecord class.
+	 *
+	 * Child classes may want to override this method to specify their relations.
+	 *
+	 * The following shows how to declare relations for a Programmer AR class:
+	 *
+	 * ~~~
+	 * return array(
+	 *     'manager:Manager' => '?.manager_id = manager.id',
+	 *     'assignments:Assignment[]' => array(
+	 *         'on' => '?.id = assignments.owner_id AND assignments.status=1',
+	 *         'orderBy' => 'assignments.create_time DESC',
+	 *     ),
+	 *     'projects:Project[]' => array(
+	 *         'via' => 'assignments',
+	 *         'on' => 'projects.id = assignments.project_id',
+	 *     ),
+	 * );
+	 * ~~~
+	 *
 	 * This method should be overridden to declare related objects.
 	 *
 	 * There are four types of relations that may exist between two active record objects:
@@ -1194,443 +1228,3 @@ abstract class ActiveRecord extends \yii\base\Model
 		return $this->__isset($offset);
 	}
 }
-
-
-/**
- * CBaseActiveRelation is the base class for all active relations.
- * @author Qiang Xue <qiang.xue@gmail.com>
- */
-class CBaseActiveRelation extends \yii\base\Component
-{
-	/**
-	 * @var string name of the related object
-	 */
-	public $name;
-	/**
-	 * @var string name of the related active record class
-	 */
-	public $className;
-	/**
-	 * @var string the foreign key in this relation
-	 */
-	public $foreignKey;
-	/**
-	 * @var mixed list of column names (an array, or a string of names separated by commas) to be selected.
-	 * Do not quote or prefix the column names unless they are used in an expression.
-	 * In that case, you should prefix the column names with 'relationName.'.
-	 */
-	public $select = '*';
-	/**
-	 * @var string WHERE clause. For {@link CActiveRelation} descendant classes, column names
-	 * referenced in the condition should be disambiguated with prefix 'relationName.'.
-	 */
-	public $condition = '';
-	/**
-	 * @var array the parameters that are to be bound to the condition.
-	 * The keys are parameter placeholder names, and the values are parameter values.
-	 */
-	public $params = array();
-	/**
-	 * @var string GROUP BY clause. For {@link CActiveRelation} descendant classes, column names
-	 * referenced in this property should be disambiguated with prefix 'relationName.'.
-	 */
-	public $group = '';
-	/**
-	 * @var string how to join with other tables. This refers to the JOIN clause in an SQL statement.
-	 * For example, <code>'LEFT JOIN users ON users.id=authorID'</code>.
-	 */
-	public $join = '';
-	/**
-	 * @var string HAVING clause. For {@link CActiveRelation} descendant classes, column names
-	 * referenced in this property should be disambiguated with prefix 'relationName.'.
-	 */
-	public $having = '';
-	/**
-	 * @var string ORDER BY clause. For {@link CActiveRelation} descendant classes, column names
-	 * referenced in this property should be disambiguated with prefix 'relationName.'.
-	 */
-	public $order = '';
-
-	/**
-	 * Constructor.
-	 * @param string $name name of the relation
-	 * @param string $className name of the related active record class
-	 * @param string $foreignKey foreign key for this relation
-	 * @param array $options additional options (name=>value). The keys must be the property names of this class.
-	 */
-	public function __construct($name, $className, $foreignKey, $options = array())
-	{
-		$this->name = $name;
-		$this->className = $className;
-		$this->foreignKey = $foreignKey;
-		foreach ($options as $name => $value)
-		{
-			$this->$name = $value;
-		}
-	}
-
-	/**
-	 * Merges this relation with a criteria specified dynamically.
-	 * @param array $criteria the dynamically specified criteria
-	 * @param boolean $fromScope whether the criteria to be merged is from scopes
-	 */
-	public function mergeWith($criteria, $fromScope = false)
-	{
-		if ($criteria instanceof CDbCriteria) {
-			$criteria = $criteria->toArray();
-		}
-		if (isset($criteria['select']) && $this->select !== $criteria['select']) {
-			if ($this->select === '*') {
-				$this->select = $criteria['select'];
-			}
-			elseif ($criteria['select'] !== '*')
-			{
-				$select1 = is_string($this->select) ? preg_split('/\s*,\s*/', trim($this->select), -1, PREG_SPLIT_NO_EMPTY) : $this->select;
-				$select2 = is_string($criteria['select']) ? preg_split('/\s*,\s*/', trim($criteria['select']), -1, PREG_SPLIT_NO_EMPTY) : $criteria['select'];
-				$this->select = array_merge($select1, array_diff($select2, $select1));
-			}
-		}
-
-		if (isset($criteria['condition']) && $this->condition !== $criteria['condition']) {
-			if ($this->condition === '') {
-				$this->condition = $criteria['condition'];
-			}
-			elseif ($criteria['condition'] !== '')
-			{
-				$this->condition = "( {$this->condition}) AND ( {$criteria['condition']})";
-			}
-		}
-
-		if (isset($criteria['params']) && $this->params !== $criteria['params']) {
-			$this->params = array_merge($this->params, $criteria['params']);
-		}
-
-		if (isset($criteria['order']) && $this->order !== $criteria['order']) {
-			if ($this->order === '') {
-				$this->order = $criteria['order'];
-			}
-			elseif ($criteria['order'] !== '')
-			{
-				$this->order = $criteria['order'] . ', ' . $this->order;
-			}
-		}
-
-		if (isset($criteria['group']) && $this->group !== $criteria['group']) {
-			if ($this->group === '') {
-				$this->group = $criteria['group'];
-			}
-			elseif ($criteria['group'] !== '')
-			{
-				$this->group .= ', ' . $criteria['group'];
-			}
-		}
-
-		if (isset($criteria['join']) && $this->join !== $criteria['join']) {
-			if ($this->join === '') {
-				$this->join = $criteria['join'];
-			}
-			elseif ($criteria['join'] !== '')
-			{
-				$this->join .= ' ' . $criteria['join'];
-			}
-		}
-
-		if (isset($criteria['having']) && $this->having !== $criteria['having']) {
-			if ($this->having === '') {
-				$this->having = $criteria['having'];
-			}
-			elseif ($criteria['having'] !== '')
-			{
-				$this->having = "( {$this->having}) AND ( {$criteria['having']})";
-			}
-		}
-	}
-}
-
-
-/**
- * CStatRelation represents a statistical relational query.
- * @author Qiang Xue <qiang.xue@gmail.com>
- */
-class CStatRelation extends CBaseActiveRelation
-{
-	/**
-	 * @var string the statistical expression. Defaults to 'COUNT(*)', meaning
-	 * the count of child objects.
-	 */
-	public $select = 'COUNT(*)';
-	/**
-	 * @var mixed the default value to be assigned to those records that do not
-	 * receive a statistical query result. Defaults to 0.
-	 */
-	public $defaultValue = 0;
-
-	/**
-	 * Merges this relation with a criteria specified dynamically.
-	 * @param array $criteria the dynamically specified criteria
-	 * @param boolean $fromScope whether the criteria to be merged is from scopes
-	 */
-	public function mergeWith($criteria, $fromScope = false)
-	{
-		if ($criteria instanceof CDbCriteria) {
-			$criteria = $criteria->toArray();
-		}
-		parent::mergeWith($criteria, $fromScope);
-
-		if (isset($criteria['defaultValue'])) {
-			$this->defaultValue = $criteria['defaultValue'];
-		}
-	}
-}
-
-
-/**
- * CActiveRelation is the base class for representing active relations that bring back related objects.
- * @author Qiang Xue <qiang.xue@gmail.com>
- * @since 2.0
- */
-class CActiveRelation extends CBaseActiveRelation
-{
-	/**
-	 * @var string join type. Defaults to 'LEFT OUTER JOIN'.
-	 */
-	public $joinType = 'LEFT OUTER JOIN';
-	/**
-	 * @var string ON clause. The condition specified here will be appended to the joining condition using AND operator.
-	 */
-	public $on = '';
-	/**
-	 * @var string the alias for the table that this relation refers to. Defaults to null, meaning
-	 * the alias will be the same as the relation name.
-	 */
-	public $alias;
-	/**
-	 * @var string|array specifies which related objects should be eagerly loaded when this related object is lazily loaded.
-	 * For more details about this property, see {@link ActiveRecord::with()}.
-	 */
-	public $with = array();
-	/**
-	 * @var boolean whether this table should be joined with the primary table.
-	 * When setting this property to be false, the table associated with this relation will
-	 * appear in a separate JOIN statement.
-	 * If this property is set true, then the corresponding table will ALWAYS be joined together
-	 * with the primary table, no matter the primary table is limited or not.
-	 * If this property is not set, the corresponding table will be joined with the primary table
-	 * only when the primary table is not limited.
-	 */
-	public $together;
-	/**
-	 * @var mixed scopes to apply
-	 * Can be set to the one of the following:
-	 * <ul>
-	 * <li>Single scope: 'scopes'=>'scopeName'.</li>
-	 * <li>Multiple scopes: 'scopes'=>array('scopeName1','scopeName2').</li>
-	 * </ul>
-	 */
-	public $scopes;
-
-	/**
-	 * Merges this relation with a criteria specified dynamically.
-	 * @param array $criteria the dynamically specified criteria
-	 * @param boolean $fromScope whether the criteria to be merged is from scopes
-	 */
-	public function mergeWith($criteria, $fromScope = false)
-	{
-		if ($criteria instanceof CDbCriteria) {
-			$criteria = $criteria->toArray();
-		}
-		if ($fromScope) {
-			if (isset($criteria['condition']) && $this->on !== $criteria['condition']) {
-				if ($this->on === '') {
-					$this->on = $criteria['condition'];
-				}
-				elseif ($criteria['condition'] !== '')
-				{
-					$this->on = "( {$this->on}) AND ( {$criteria['condition']})";
-				}
-			}
-			unset($criteria['condition']);
-		}
-
-		parent::mergeWith($criteria);
-
-		if (isset($criteria['joinType'])) {
-			$this->joinType = $criteria['joinType'];
-		}
-
-		if (isset($criteria['on']) && $this->on !== $criteria['on']) {
-			if ($this->on === '') {
-				$this->on = $criteria['on'];
-			}
-			elseif ($criteria['on'] !== '')
-			{
-				$this->on = "( {$this->on}) AND ( {$criteria['on']})";
-			}
-		}
-
-		if (isset($criteria['with'])) {
-			$this->with = $criteria['with'];
-		}
-
-		if (isset($criteria['alias'])) {
-			$this->alias = $criteria['alias'];
-		}
-
-		if (isset($criteria['together'])) {
-			$this->together = $criteria['together'];
-		}
-	}
-}
-
-
-/**
- * CBelongsToRelation represents the parameters specifying a BELONGS_TO relation.
- * @author Qiang Xue <qiang.xue@gmail.com>
- * @since 2.0
- */
-class CBelongsToRelation extends CActiveRelation
-{
-}
-
-
-/**
- * CHasOneRelation represents the parameters specifying a HAS_ONE relation.
- * @author Qiang Xue <qiang.xue@gmail.com>
- * @since 2.0
- */
-class CHasOneRelation extends CActiveRelation
-{
-	/**
-	 * @var string the name of the relation that should be used as the bridge to this relation.
-	 * Defaults to null, meaning don't use any bridge.
-	 */
-	public $through;
-}
-
-
-/**
- * CHasManyRelation represents the parameters specifying a HAS_MANY relation.
- * @author Qiang Xue <qiang.xue@gmail.com>
- * @since 2.0
- */
-class CHasManyRelation extends CActiveRelation
-{
-	/**
-	 * @var integer limit of the rows to be selected. It is effective only for lazy loading this related object. Defaults to -1, meaning no limit.
-	 */
-	public $limit = -1;
-	/**
-	 * @var integer offset of the rows to be selected. It is effective only for lazy loading this related object. Defaults to -1, meaning no offset.
-	 */
-	public $offset = -1;
-	/**
-	 * @var string the name of the column that should be used as the key for storing related objects.
-	 * Defaults to null, meaning using zero-based integer IDs.
-	 */
-	public $index;
-	/**
-	 * @var string the name of the relation that should be used as the bridge to this relation.
-	 * Defaults to null, meaning don't use any bridge.
-	 */
-	public $through;
-
-	/**
-	 * Merges this relation with a criteria specified dynamically.
-	 * @param array $criteria the dynamically specified criteria
-	 * @param boolean $fromScope whether the criteria to be merged is from scopes
-	 */
-	public function mergeWith($criteria, $fromScope = false)
-	{
-		if ($criteria instanceof CDbCriteria) {
-			$criteria = $criteria->toArray();
-		}
-		parent::mergeWith($criteria, $fromScope);
-		if (isset($criteria['limit']) && $criteria['limit'] > 0) {
-			$this->limit = $criteria['limit'];
-		}
-
-		if (isset($criteria['offset']) && $criteria['offset'] >= 0) {
-			$this->offset = $criteria['offset'];
-		}
-
-		if (isset($criteria['index'])) {
-			$this->index = $criteria['index'];
-		}
-	}
-}
-
-
-/**
- * CManyManyRelation represents the parameters specifying a MANY_MANY relation.
- * @author Qiang Xue <qiang.xue@gmail.com>
- * @since 2.0
- */
-class CManyManyRelation extends CHasManyRelation
-{
-}
-
-
-/**
- * ActiveMetaData represents the meta-data for an Active Record class.
- *
- * @author Qiang Xue <qiang.xue@gmail.com>
- * @since 2.0
- */
-class ActiveMetaData
-{
-	/**
-	 * @var TableSchema the table schema information
-	 */
-	public $table;
-	/**
-	 * @var array list of relations
-	 */
-	public $relations = array();
-
-	/**
-	 * Constructor.
-	 * @param string $modelClass the model class name
-	 */
-	public function __construct($modelClass)
-	{
-		$tableName = $modelClass::tableName();
-		$table = $modelClass::getDbConnection()->getDriver()->getTableSchema($tableName);
-		if ($table === null) {
-			throw new Exception("Unable to find table '$tableName' for ActiveRecord class '$modelClass'.");
-		}
-		if ($table->primaryKey === null) {
-			$primaryKey = $modelClass::primaryKey();
-			if ($primaryKey !== null) {
-				$table->fixPrimaryKey($primaryKey);
-			} else {
-				throw new Exception("The table '$tableName' for ActiveRecord class '$modelClass' does not have a primary key.");
-			}
-		}
-		$this->table = $table;
-
-		foreach ($modelClass::relations() as $name => $config) {
-			$this->addRelation($name, $config);
-		}
-	}
-
-	/**
-	 * Adds a relation.
-	 *
-	 * $config is an array with three elements:
-	 * relation type, the related active record class and the foreign key.
-	 *
-	 * @throws Exception
-	 * @param string $name $name Name of the relation.
-	 * @param array $config $config Relation parameters.
-	 * @return void
-	 */
-	public function addRelation($name, $config)
-	{
-		// relation class, AR class, FK
-		if (isset($config[0], $config[1], $config[2])) {
-			$this->relations[$name] = new $config[0]($name, $config[1], $config[2], array_slice($config, 3));
-		} else {
-			throw new Exception(Yii::t('yii', 'Active record "{class}" has an invalid configuration for relation "{relation}". It must specify the relation type, the related active record class and the foreign key.', array('{class}' => get_class($this->_model), '{relation}' => $name)));
-		}
-	}
-}
diff --git a/framework/db/ar/ActiveRelation.php b/framework/db/ar/ActiveRelation.php
new file mode 100644
index 0000000..0de0e84
--- /dev/null
+++ b/framework/db/ar/ActiveRelation.php
@@ -0,0 +1,43 @@
+<?php
+
+namespace yii\db\ar;
+
+class ActiveRelation extends \yii\db\dao\BaseQuery
+{
+	public $name;
+	public $modelClass;
+	public $hasMany;
+
+	public $joinType;
+	public $alias;
+	public $on;
+	public $via;
+	public $index;
+	public $with;
+	public $scopes;
+
+	public function mergeWith($relation)
+	{
+		parent::mergeWith($relation);
+		if ($relation->joinType !== null) {
+			$this->joinType = $relation->joinType;
+		}
+		if ($relation->alias !== null) {
+			$this->alias = $relation->alias;
+		}
+		if ($relation->on !== null) {
+			if (!empty($this->on)) {
+				$this->on = "({$this->on}) AND ({$relation->on})";
+			} else {
+				$this->on = $relation->on;
+			}
+		}
+		if ($relation->via !== null) {
+			$this->via = $relation->via;
+		}
+		if ($relation->index !== null) {
+			$this->index = $relation->index;
+		}
+		// todo: with, scopes
+	}
+}
diff --git a/framework/db/dao/BaseQuery.php b/framework/db/dao/BaseQuery.php
new file mode 100644
index 0000000..82a2431
--- /dev/null
+++ b/framework/db/dao/BaseQuery.php
@@ -0,0 +1,715 @@
+<?php
+/**
+ * BaseQuery class file.
+ *
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright &copy; 2008-2012 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\db\dao;
+
+/**
+ * Query represents a SQL statement in a way that is independent of DBMS.
+ *
+ * Query not only can represent a SELECT statement, it can also represent INSERT, UPDATE, DELETE,
+ * and other commonly used DDL statements, such as CREATE TABLE, CREATE INDEX, etc.
+ *
+ * Query provides a set of methods to facilitate the specification of different clauses.
+ * These methods can be chained together. For example,
+ *
+ * ~~~
+ * $query = new Query;
+ * $query->select('id, name')
+ *     ->from('tbl_user')
+ *     ->limit(10);
+ * // get the actual SQL statement
+ * echo $query->getSql();
+ * // or execute the query
+ * $users = $query->createCommand()->queryAll();
+ * ~~~
+ *
+ * By calling [[getSql()]], we can obtain the actual SQL statement from a Query object.
+ * And by calling [[createCommand()]], we can get a [[Command]] instance which can be further
+ * used to perform/execute the DB query against a database.
+ *
+ * @property string $sql the SQL statement represented by this query object.
+ *
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class BaseQuery extends \yii\base\Object
+{
+	/**
+	 * @var string|array the columns being selected. This refers to the SELECT clause in a SQL
+	 * statement. It can be either a string (e.g. `'id, name'`) or an array (e.g. `array('id', 'name')`).
+	 * If not set, if means all columns.
+	 * @see select()
+	 */
+	public $select;
+	/**
+	 * @var string additional option that should be appended to the 'SELECT' keyword. For example,
+	 * in MySQL, the option 'SQL_CALC_FOUND_ROWS' can be used.
+	 */
+	public $selectOption;
+	/**
+	 * @var boolean whether to select distinct rows of data only. If this is set true,
+	 * the SELECT clause would be changed to SELECT DISTINCT.
+	 */
+	public $distinct;
+	/**
+	 * @var string|array the table(s) to be selected from. This refers to the FROM clause in a SQL statement.
+	 * It can be either a string (e.g. `'tbl_user, tbl_post'`) or an array (e.g. `array('tbl_user', 'tbl_post')`).
+	 * @see from()
+	 */
+	public $from;
+	/**
+	 * @var string|array query condition. This refers to the WHERE clause in a SQL statement.
+	 * For example, `age > 31 AND team = 1`.
+	 * @see where()
+	 */
+	public $where;
+	/**
+	 * @var integer maximum number of records to be returned. If not set or less than 0, it means no limit.
+	 */
+	public $limit;
+	/**
+	 * @var integer zero-based offset from where the records are to be returned. If not set or
+	 * less than 0, it means starting from the beginning.
+	 */
+	public $offset;
+	/**
+	 * @var string|array how to sort the query results. This refers to the ORDER BY clause in a SQL statement.
+	 * It can be either a string (e.g. `'id ASC, name DESC'`) or an array (e.g. `array('id ASC', 'name DESC')`).
+	 */
+	public $orderBy;
+	/**
+	 * @var string|array how to group the query results. This refers to the GROUP BY clause in a SQL statement.
+	 * It can be either a string (e.g. `'company, department'`) or an array (e.g. `array('company', 'department')`).
+	 */
+	public $groupBy;
+	/**
+	 * @var string|array how to join with other tables. This refers to the JOIN clause in a SQL statement.
+	 * It can either a string (e.g. `'LEFT JOIN tbl_user ON tbl_user.id=author_id'`) or an array (e.g.
+	 * `array('LEFT JOIN tbl_user ON tbl_user.id=author_id', 'LEFT JOIN tbl_team ON tbl_team.id=team_id')`).
+	 * @see join()
+	 */
+	public $join;
+	/**
+	 * @var string|array the condition to be applied in the GROUP BY clause.
+	 * It can be either a string or an array. Please refer to [[where()]] on how to specify the condition.
+	 */
+	public $having;
+	/**
+	 * @var array list of query parameter values indexed by parameter placeholders.
+	 * For example, `array(':name'=>'Dan', ':age'=>31)`.
+	 */
+	public $params;
+	/**
+	 * @var string|array the UNION clause(s) in a SQL statement. This can be either a string
+	 * representing a single UNION clause or an array representing multiple UNION clauses.
+	 * Each union clause can be a string or a `Query` object which refers to the SQL statement.
+	 */
+	public $union;
+
+	/**
+	 * Sets the SELECT part of the query.
+	 * @param mixed $columns the columns to be selected. Defaults to '*', meaning all columns.
+	 * Columns can be specified in either a string (e.g. "id, name") or an array (e.g. array('id', 'name')).
+	 * Columns can contain table prefixes (e.g. "tbl_user.id") and/or column aliases (e.g. "tbl_user.id AS user_id").
+	 * The method will automatically quote the column names unless a column contains some parenthesis
+	 * (which means the column contains a DB expression).
+	 * @param boolean $distinct whether to use 'SELECT DISTINCT'.
+	 * @param string $option additional option that should be appended to the 'SELECT' keyword. For example,
+	 * in MySQL, the option 'SQL_CALC_FOUND_ROWS' can be used.
+	 * @return Query the query object itself
+	 */
+	public function select($columns = '*', $distinct = false, $option = '')
+	{
+		$this->select = $columns;
+		$this->distinct = $distinct;
+		$this->selectOption = $option;
+		return $this;
+	}
+
+	/**
+	 * Sets the FROM part of the query.
+	 * @param mixed $tables the table(s) to be selected from. This can be either a string (e.g. 'tbl_user')
+	 * or an array (e.g. array('tbl_user', 'tbl_profile')) specifying one or several table names.
+	 * Table names can contain schema prefixes (e.g. 'public.tbl_user') and/or table aliases (e.g. 'tbl_user u').
+	 * The method will automatically quote the table names unless it contains some parenthesis
+	 * (which means the table is given as a sub-query or DB expression).
+	 * @return Query the query object itself
+	 */
+	public function from($tables)
+	{
+		$this->from = $tables;
+		return $this;
+	}
+
+	/**
+	 * Sets the WHERE part of the query.
+	 *
+	 * The method requires a $condition parameter, and optionally a $params parameter
+	 * specifying the values to be bound to the query.
+	 *
+	 * The $condition parameter should be either a string (e.g. 'id=1') or an array.
+	 * If the latter, it must be in one of the following two formats:
+	 *
+	 * - hash format: `array('column1' => value1, 'column2' => value2, ...)`
+	 * - operator format: `array(operator, operand1, operand2, ...)`
+	 *
+	 * A condition in hash format represents the following SQL expression in general:
+	 * `column1=value1 AND column2=value2 AND ...`. In case when a value is an array,
+	 * an `IN` expression will be generated. And if a value is null, `IS NULL` will be used
+	 * in the generated expression. Below are some examples:
+	 *
+	 * - `array('type'=>1, 'status'=>2)` generates `(type=1) AND (status=2)`.
+	 * - `array('id'=>array(1,2,3), 'status'=>2)` generates `(id IN (1,2,3)) AND (status=2)`.
+	 * - `array('status'=>null) generates `status IS NULL`.
+	 *
+	 * A condition in operator format generates the SQL expression according to the specified operator, which
+	 * can be one of the followings:
+	 *
+	 * - `and`: the operands should be concatenated together using `AND`. For example,
+	 * `array('and', 'id=1', 'id=2')` will generate `id=1 AND id=2`. If an operand is an array,
+	 * it will be converted into a string using the rules described here. For example,
+	 * `array('and', 'type=1', array('or', 'id=1', 'id=2'))` will generate `type=1 AND (id=1 OR id=2)`.
+	 * The method will NOT do any quoting or escaping.
+	 *
+	 * - `or`: similar to the `and` operator except that the operands are concatenated using `OR`.
+	 *
+	 * - `between`: operand 1 should be the column name, and operand 2 and 3 should be the
+	 * starting and ending values of the range that the column is in.
+	 * For example, `array('between', 'id', 1, 10)` will generate `id BETWEEN 1 AND 10`.
+	 *
+	 * - `not between`: similar to `between` except the `BETWEEN` is replaced with `NOT BETWEEN`
+	 * in the generated condition.
+	 *
+	 * - `in`: operand 1 should be a column or DB expression, and operand 2 be an array representing
+	 * the range of the values that the column or DB expression should be in. For example,
+	 * `array('in', 'id', array(1,2,3))` will generate `id IN (1,2,3)`.
+	 * The method will properly quote the column name and escape values in the range.
+	 *
+	 * - `not in`: similar to the `in` operator except that `IN` is replaced with `NOT IN` in the generated condition.
+	 *
+	 * - `like`: operand 1 should be a column or DB expression, and operand 2 be a string or an array representing
+	 * the values that the column or DB expression should be like.
+	 * For example, `array('like', 'name', '%tester%')` will generate `name LIKE '%tester%'`.
+	 * When the value range is given as an array, multiple `LIKE` predicates will be generated and concatenated
+	 * using `AND`. For example, `array('like', 'name', array('%test%', '%sample%'))` will generate
+	 * `name LIKE '%test%' AND name LIKE '%sample%'`.
+	 * The method will properly quote the column name and escape values in the range.
+	 *
+	 * - `or like`: similar to the `like` operator except that `OR` is used to concatenate the `LIKE`
+	 * predicates when operand 2 is an array.
+	 *
+	 * - `not like`: similar to the `like` operator except that `LIKE` is replaced with `NOT LIKE`
+	 * in the generated condition.
+	 *
+	 * - `or not like`: similar to the `not like` operator except that `OR` is used to concatenate
+	 * the `NOT LIKE` predicates.
+	 *
+	 * @param string|array $condition the conditions that should be put in the WHERE part.
+	 * @param array $params the parameters (name=>value) to be bound to the query.
+	 * For anonymous parameters, they can alternatively be specified as separate parameters to this method.
+	 * For example, `where('type=? AND status=?', 100, 1)`.
+	 * @return Query the query object itself
+	 * @see andWhere()
+	 * @see orWhere()
+	 */
+	public function where($condition, $params = array())
+	{
+		$this->where = $condition;
+		if (!is_array($params)) {
+			$params = func_get_args();
+			unset($params[0]);
+		}
+		$this->addParams($params);
+		return $this;
+	}
+
+	/**
+	 * Adds an additional WHERE condition to the existing one.
+	 * The new condition and the existing one will be joined using the 'AND' operator.
+	 * @param string|array $condition the new WHERE condition. Please refer to [[where()]]
+	 * on how to specify this parameter.
+	 * @param array $params the parameters (name=>value) to be bound to the query.
+	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
+	 * @return Query the query object itself
+	 * @see where()
+	 * @see orWhere()
+	 */
+	public function andWhere($condition, $params = array())
+	{
+		if ($this->where === null) {
+			$this->where = $condition;
+		} else {
+			$this->where = array('and', $this->where, $condition);
+		}
+		if (!is_array($params)) {
+			$params = func_get_args();
+			unset($params[0]);
+		}
+		$this->addParams($params);
+		return $this;
+	}
+
+	/**
+	 * Adds an additional WHERE condition to the existing one.
+	 * The new condition and the existing one will be joined using the 'OR' operator.
+	 * @param string|array $condition the new WHERE condition. Please refer to [[where()]]
+	 * on how to specify this parameter.
+	 * @param array $params the parameters (name=>value) to be bound to the query.
+	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
+	 * @return Query the query object itself
+	 * @see where()
+	 * @see andWhere()
+	 */
+	public function orWhere($condition, $params = array())
+	{
+		if ($this->where === null) {
+			$this->where = $condition;
+		} else {
+			$this->where = array('or', $this->where, $condition);
+		}
+		if (!is_array($params)) {
+			$params = func_get_args();
+			unset($params[0]);
+		}
+		$this->addParams($params);
+		return $this;
+	}
+
+	/**
+	 * Appends an INNER JOIN part to the query.
+	 * @param string $table the table to be joined.
+	 * Table name can contain schema prefix (e.g. 'public.tbl_user') and/or table alias (e.g. 'tbl_user u').
+	 * The method will automatically quote the table name unless it contains some parenthesis
+	 * (which means the table is given as a sub-query or DB expression).
+	 * @param string|array $condition the join condition that should appear in the ON part.
+	 * Please refer to [[where()]] on how to specify this parameter.
+	 * @param array $params the parameters (name=>value) to be bound to the query.
+	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
+	 * @return Query the query object itself
+	 */
+	public function join($table, $condition, $params = array())
+	{
+		$this->join[] = array('JOIN', $table, $condition);
+		if (!is_array($params)) {
+			$params = func_get_args();
+			array_shift($params);
+			unset($params[0]);
+		}
+		return $this->addParams($params);
+	}
+
+	/**
+	 * Appends a LEFT OUTER JOIN part to the query.
+	 * @param string $table the table to be joined.
+	 * Table name can contain schema prefix (e.g. 'public.tbl_user') and/or table alias (e.g. 'tbl_user u').
+	 * The method will automatically quote the table name unless it contains some parenthesis
+	 * (which means the table is given as a sub-query or DB expression).
+	 * @param string|array $condition the join condition that should appear in the ON part.
+	 * Please refer to [[where()]] on how to specify this parameter.
+	 * @param array $params the parameters (name=>value) to be bound to the query
+	 * @return Query the query object itself
+	 */
+	public function leftJoin($table, $condition, $params = array())
+	{
+		$this->join[] = array('LEFT JOIN', $table, $condition);
+		if (!is_array($params)) {
+			$params = func_get_args();
+			array_shift($params);
+			unset($params[0]);
+		}
+		return $this->addParams($params);
+	}
+
+	/**
+	 * Appends a RIGHT OUTER JOIN part to the query.
+	 * @param string $table the table to be joined.
+	 * Table name can contain schema prefix (e.g. 'public.tbl_user') and/or table alias (e.g. 'tbl_user u').
+	 * The method will automatically quote the table name unless it contains some parenthesis
+	 * (which means the table is given as a sub-query or DB expression).
+	 * @param string|array $condition the join condition that should appear in the ON part.
+	 * Please refer to [[where()]] on how to specify this parameter.
+	 * @param array $params the parameters (name=>value) to be bound to the query
+	 * @return Query the query object itself
+	 */
+	public function rightJoin($table, $condition, $params = array())
+	{
+		$this->join[] = array('RIGHT JOIN', $table, $condition);
+		if (!is_array($params)) {
+			$params = func_get_args();
+			array_shift($params);
+			unset($params[0]);
+		}
+		return $this->addParams($params);
+	}
+
+	/**
+	 * Appends a CROSS JOIN part to the query.
+	 * Note that not all DBMS support CROSS JOIN.
+	 * @param string $table the table to be joined.
+	 * Table name can contain schema prefix (e.g. 'public.tbl_user') and/or table alias (e.g. 'tbl_user u').
+	 * The method will automatically quote the table name unless it contains some parenthesis
+	 * (which means the table is given as a sub-query or DB expression).
+	 * @return Query the query object itself
+	 */
+	public function crossJoin($table)
+	{
+		$this->join[] = array('CROSS JOIN', $table);
+		return $this;
+	}
+
+	/**
+	 * Appends a NATURAL JOIN part to the query.
+	 * Note that not all DBMS support NATURAL JOIN.
+	 * @param string $table the table to be joined.
+	 * Table name can contain schema prefix (e.g. 'public.tbl_user') and/or table alias (e.g. 'tbl_user u').
+	 * The method will automatically quote the table name unless it contains some parenthesis
+	 * (which means the table is given as a sub-query or DB expression).
+	 * @return Query the query object itself
+	 */
+	public function naturalJoin($table)
+	{
+		$this->join[] = array('NATURAL JOIN', $table);
+		return $this;
+	}
+
+	/**
+	 * Sets the GROUP BY part of the query.
+	 * @param string|array $columns the columns to be grouped by.
+	 * Columns can be specified in either a string (e.g. "id, name") or an array (e.g. array('id', 'name')).
+	 * The method will automatically quote the column names unless a column contains some parenthesis
+	 * (which means the column contains a DB expression).
+	 * @return Query the query object itself
+	 * @see addGroupBy()
+	 */
+	public function groupBy($columns)
+	{
+		$this->groupBy = $columns;
+		return $this;
+	}
+
+	/**
+	 * Adds additional group-by columns to the existing ones.
+	 * @param string|array $columns additional columns to be grouped by.
+	 * Columns can be specified in either a string (e.g. "id, name") or an array (e.g. array('id', 'name')).
+	 * The method will automatically quote the column names unless a column contains some parenthesis
+	 * (which means the column contains a DB expression).
+	 * @return Query the query object itself
+	 * @see groupBy()
+	 */
+	public function addGroupBy($columns)
+	{
+		if (empty($this->groupBy)) {
+			$this->groupBy = $columns;
+		} else {
+			if (!is_array($this->groupBy)) {
+				$this->groupBy = preg_split('/\s*,\s*/', trim($this->groupBy), -1, PREG_SPLIT_NO_EMPTY);
+			}
+			if (!is_array($columns)) {
+				$columns = preg_split('/\s*,\s*/', trim($columns), -1, PREG_SPLIT_NO_EMPTY);
+			}
+			$this->groupBy = array_merge($this->groupBy, $columns);
+		}
+		return $this;
+	}
+
+	/**
+	 * Sets the HAVING part of the query.
+	 * @param string|array $condition the conditions to be put after HAVING.
+	 * Please refer to [[where()]] on how to specify this parameter.
+	 * @param array $params the parameters (name=>value) to be bound to the query.
+	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
+	 * @return Query the query object itself
+	 * @see andHaving()
+	 * @see orHaving()
+	 */
+	public function having($condition, $params = array())
+	{
+		$this->having = $condition;
+		if (!is_array($params)) {
+			$params = func_get_args();
+			unset($params[0]);
+		}
+		$this->addParams($params);
+		return $this;
+	}
+
+	/**
+	 * Adds an additional HAVING condition to the existing one.
+	 * The new condition and the existing one will be joined using the 'AND' operator.
+	 * @param string|array $condition the new HAVING condition. Please refer to [[where()]]
+	 * on how to specify this parameter.
+	 * @param array $params the parameters (name=>value) to be bound to the query.
+	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
+	 * @return Query the query object itself
+	 * @see having()
+	 * @see orHaving()
+	 */
+	public function andHaving($condition, $params = array())
+	{
+		if ($this->having === null) {
+			$this->having = $condition;
+		} else {
+			$this->having = array('and', $this->having, $condition);
+		}
+		if (!is_array($params)) {
+			$params = func_get_args();
+			unset($params[0]);
+		}
+		$this->addParams($params);
+		return $this;
+	}
+
+	/**
+	 * Adds an additional HAVING condition to the existing one.
+	 * The new condition and the existing one will be joined using the 'OR' operator.
+	 * @param string|array $condition the new HAVING condition. Please refer to [[where()]]
+	 * on how to specify this parameter.
+	 * @param array $params the parameters (name=>value) to be bound to the query.
+	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
+	 * @return Query the query object itself
+	 * @see having()
+	 * @see andHaving()
+	 */
+	public function orHaving($condition, $params = array())
+	{
+		if ($this->having === null) {
+			$this->having = $condition;
+		} else {
+			$this->having = array('or', $this->having, $condition);
+		}
+		if (!is_array($params)) {
+			$params = func_get_args();
+			unset($params[0]);
+		}
+		$this->addParams($params);
+		return $this;
+	}
+
+	/**
+	 * Sets the ORDER BY part of the query.
+	 * @param string|array $columns the columns (and the directions) to be ordered by.
+	 * Columns can be specified in either a string (e.g. "id ASC, name DESC") or an array (e.g. array('id ASC', 'name DESC')).
+	 * The method will automatically quote the column names unless a column contains some parenthesis
+	 * (which means the column contains a DB expression).
+	 * @return Query the query object itself
+	 * @see addOrderBy()
+	 */
+	public function orderBy($columns)
+	{
+		$this->orderBy = $columns;
+		return $this;
+	}
+
+	/**
+	 * Adds additional ORDER BY columns to the query.
+	 * @param string|array $columns the columns (and the directions) to be ordered by.
+	 * Columns can be specified in either a string (e.g. "id ASC, name DESC") or an array (e.g. array('id ASC', 'name DESC')).
+	 * The method will automatically quote the column names unless a column contains some parenthesis
+	 * (which means the column contains a DB expression).
+	 * @return Query the query object itself
+	 * @see orderBy()
+	 */
+	public function addOrderBy($columns)
+	{
+		if (empty($this->orderBy)) {
+			$this->orderBy = $columns;
+		} else {
+			if (!is_array($this->orderBy)) {
+				$this->orderBy = preg_split('/\s*,\s*/', trim($this->orderBy), -1, PREG_SPLIT_NO_EMPTY);
+			}
+			if (!is_array($columns)) {
+				$columns = preg_split('/\s*,\s*/', trim($columns), -1, PREG_SPLIT_NO_EMPTY);
+			}
+			$this->orderBy = array_merge($this->orderBy, $columns);
+		}
+		return $this;
+	}
+
+	/**
+	 * Sets the LIMIT part of the query.
+	 * @param integer $limit the limit
+	 * @return Query the query object itself
+	 */
+	public function limit($limit)
+	{
+		$this->limit = $limit;
+		return $this;
+	}
+
+	/**
+	 * Sets the OFFSET part of the query.
+	 * @param integer $offset the offset
+	 * @return Query the query object itself
+	 */
+	public function offset($offset)
+	{
+		$this->offset = $offset;
+		return $this;
+	}
+
+	/**
+	 * Appends a SQL statement using UNION operator.
+	 * @param string $sql the SQL statement to be appended using UNION
+	 * @return Query the query object itself
+	 */
+	public function union($sql)
+	{
+		$this->union[] = $sql;
+		return $this;
+	}
+
+	/**
+	 * Sets the parameters to be bound to the query.
+	 * @param array list of query parameter values indexed by parameter placeholders.
+	 * For example, `array(':name'=>'Dan', ':age'=>31)`.
+	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
+	 * @return Query the query object itself
+	 * @see addParams()
+	 */
+	public function params($params)
+	{
+		$this->params = $params;
+		return $this;
+	}
+
+	/**
+	 * Adds additional parameters to be bound to the query.
+	 * @param array list of query parameter values indexed by parameter placeholders.
+	 * For example, `array(':name'=>'Dan', ':age'=>31)`.
+	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
+	 * @return Query the query object itself
+	 * @see params()
+	 */
+	public function addParams($params)
+	{
+		if ($this->params === null) {
+			$this->params = $params;
+		} else {
+			foreach ($params as $name => $value) {
+				if (is_integer($name)) {
+					$this->params[] = $value;
+				} else {
+					$this->params[$name] = $value;
+				}
+			}
+		}
+		return $this;
+	}
+
+	/**
+	 * Merges this query with another one.
+	 *
+	 * The merging is done according to the following rules:
+	 *
+	 * - [[select]]: the union of both queries' [[select]] property values.
+	 * - [[selectOption]], [[distinct]], [[limit]], [[offset]]: the new query
+	 * takes precedence over this query.
+	 *  - [[where]], [[having]]: the new query's corresponding property value
+	 * will be 'AND' together with the existing one.
+	 * - [[params]], [[orderBy]], [[groupBy]], [[join]], [[union]]: the new query's
+	 * corresponding property value will be appended to the existing one.
+	 *
+	 * In general, the merging makes the resulting query more restrictive and specific.
+	 * @param BaseQuery $query the new query to be merged with this query.
+	 * @return BaseQuery the query object itself
+	 */
+	public function mergeWith($query)
+	{
+		if ($this->select !== $query->select) {
+			if (empty($this->select)) {
+				$this->select = $query->select;
+			} elseif (!empty($query->select)) {
+				$select1 = is_string($this->select) ? preg_split('/\s*,\s*/', trim($this->select), -1, PREG_SPLIT_NO_EMPTY) : $this->select;
+				$select2 = is_string($query->select) ? preg_split('/\s*,\s*/', trim($query->select), -1, PREG_SPLIT_NO_EMPTY) : $query->select;
+				$this->select = array_merge($select1, array_diff($select2, $select1));
+			}
+		}
+
+		if ($query->selectOption !== null) {
+			$this->selectOption = $query->selectOption;
+		}
+
+		if ($query->distinct !== null) {
+			$this->distinct = $query->distinct;
+		}
+
+		if ($query->limit !== null) {
+			$this->limit = $query->limit;
+		}
+
+		if ($query->offset !== null) {
+			$this->offset = $query->offset;
+		}
+
+		if ($query->where !== null) {
+			$this->andWhere($query->where);
+		}
+
+		if ($query->having !== null) {
+			$this->andHaving($query->having);
+		}
+
+		if ($query->params !== null) {
+			$this->addParams($query->params);
+		}
+
+		if ($query->orderBy !== null) {
+			$this->addOrderBy($query->orderBy);
+		}
+
+		if ($query->groupBy !== null) {
+			$this->addGroupBy($query->groupBy);
+		}
+
+		if ($query->join !== null) {
+			if (empty($this->join)) {
+				$this->join = $query->join;
+			} else {
+				if (!is_array($this->join)) {
+					$this->join = array($this->join);
+				}
+				if (is_array($query->join)) {
+					$this->join = array_merge($this->join, $query->join);
+				} else {
+					$this->join[] = $query->join;
+				}
+			}
+		}
+
+		if ($query->union !== null) {
+			if (empty($this->union)) {
+				$this->union = $query->union;
+			} else {
+				if (!is_array($this->union)) {
+					$this->union = array($this->union);
+				}
+				if (is_array($query->union)) {
+					$this->union = array_merge($this->union, $query->union);
+				} else {
+					$this->union[] = $query->union;
+				}
+			}
+		}
+
+		return $this;
+	}
+
+	/**
+	 * Resets the query object to its original state.
+	 * @return Query the query object itself
+	 */
+	public function reset()
+	{
+		foreach (get_object_vars($this) as $name => $value) {
+			$this->$name = null;
+		}
+		return $this;
+	}
+}
diff --git a/framework/db/dao/Query.php b/framework/db/dao/Query.php
index 24858bb..d48744e 100644
--- a/framework/db/dao/Query.php
+++ b/framework/db/dao/Query.php
@@ -39,80 +39,9 @@ namespace yii\db\dao;
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
-class Query extends \yii\base\Object
+class Query extends BaseQuery
 {
 	/**
-	 * @var string|array the columns being selected. This refers to the SELECT clause in a SQL
-	 * statement. It can be either a string (e.g. `'id, name'`) or an array (e.g. `array('id', 'name')`).
-	 * If not set, if means all columns.
-	 * @see select()
-	 */
-	public $select;
-	/**
-	 * @var string additional option that should be appended to the 'SELECT' keyword. For example,
-	 * in MySQL, the option 'SQL_CALC_FOUND_ROWS' can be used.
-	 */
-	public $selectOption;
-	/**
-	 * @var string|array the table(s) to be selected from. This refers to the FROM clause in a SQL statement.
-	 * It can be either a string (e.g. `'tbl_user, tbl_post'`) or an array (e.g. `array('tbl_user', 'tbl_post')`).
-	 * @see from()
-	 */
-	public $from;
-	/**
-	 * @var boolean whether to select distinct rows of data only. If this is set true,
-	 * the SELECT clause would be changed to SELECT DISTINCT.
-	 */
-	public $distinct;
-	/**
-	 * @var string|array query condition. This refers to the WHERE clause in a SQL statement.
-	 * For example, `age > 31 AND team = 1`.
-	 * @see where()
-	 */
-	public $where;
-	/**
-	 * @var integer maximum number of records to be returned. If not set or less than 0, it means no limit.
-	 */
-	public $limit;
-	/**
-	 * @var integer zero-based offset from where the records are to be returned. If not set or
-	 * less than 0, it means starting from the beginning.
-	 */
-	public $offset;
-	/**
-	 * @var string|array how to sort the query results. This refers to the ORDER BY clause in a SQL statement.
-	 * It can be either a string (e.g. `'id ASC, name DESC'`) or an array (e.g. `array('id ASC', 'name DESC')`).
-	 */
-	public $orderBy;
-	/**
-	 * @var string|array how to group the query results. This refers to the GROUP BY clause in a SQL statement.
-	 * It can be either a string (e.g. `'company, department'`) or an array (e.g. `array('company', 'department')`).
-	 */
-	public $groupBy;
-	/**
-	 * @var string|array how to join with other tables. This refers to the JOIN clause in a SQL statement.
-	 * It can either a string (e.g. `'LEFT JOIN tbl_user ON tbl_user.id=author_id'`) or an array (e.g.
-	 * `array('LEFT JOIN tbl_user ON tbl_user.id=author_id', 'LEFT JOIN tbl_team ON tbl_team.id=team_id')`).
-	 * @see join()
-	 */
-	public $join;
-	/**
-	 * @var string|array the condition to be applied in the GROUP BY clause.
-	 * It can be either a string or an array. Please refer to [[where()]] on how to specify the condition.
-	 */
-	public $having;
-	/**
-	 * @var array list of query parameter values indexed by parameter placeholders.
-	 * For example, `array(':name'=>'Dan', ':age'=>31)`.
-	 */
-	public $params;
-	/**
-	 * @var string|array the UNION clause(s) in a SQL statement. This can be either a string
-	 * representing a single UNION clause or an array representing multiple UNION clauses.
-	 * Each union clause can be a string or a `Query` object which refers to the SQL statement.
-	 */
-	public $union;
-	/**
 	 * @var array the operation that this query represents. This refers to the method call as well as
 	 * the corresponding parameters for constructing a non-query SQL statement (e.g. INSERT, CREATE TABLE).
 	 * This property is mainly maintained by methods such as [[insert()]], [[update()]], [[createTable()]].
@@ -120,497 +49,33 @@ class Query extends \yii\base\Object
 	 */
 	public $operation;
 
-	/**
-	/**
-	 * Sets the SELECT part of the query.
-	 * @param mixed $columns the columns to be selected. Defaults to '*', meaning all columns.
-	 * Columns can be specified in either a string (e.g. "id, name") or an array (e.g. array('id', 'name')).
-	 * Columns can contain table prefixes (e.g. "tbl_user.id") and/or column aliases (e.g. "tbl_user.id AS user_id").
-	 * The method will automatically quote the column names unless a column contains some parenthesis
-	 * (which means the column contains a DB expression).
-	 * @param boolean $distinct whether to use 'SELECT DISTINCT'.
-	 * @param string $option additional option that should be appended to the 'SELECT' keyword. For example,
-	 * in MySQL, the option 'SQL_CALC_FOUND_ROWS' can be used.
-	 * @return Query the query object itself
-	 */
-	public function select($columns = '*', $distinct = false, $option = '')
-	{
-		$this->select = $columns;
-		$this->distinct = $distinct;
-		$this->selectOption = $option;
-		return $this;
-	}
-
-	/**
-	 * Sets the FROM part of the query.
-	 * @param mixed $tables the table(s) to be selected from. This can be either a string (e.g. 'tbl_user')
-	 * or an array (e.g. array('tbl_user', 'tbl_profile')) specifying one or several table names.
-	 * Table names can contain schema prefixes (e.g. 'public.tbl_user') and/or table aliases (e.g. 'tbl_user u').
-	 * The method will automatically quote the table names unless it contains some parenthesis
-	 * (which means the table is given as a sub-query or DB expression).
-	 * @return Query the query object itself
-	 */
-	public function from($tables)
-	{
-		$this->from = $tables;
-		return $this;
-	}
-
-	/**
-	 * Sets the WHERE part of the query.
-	 *
-	 * The method requires a $condition parameter, and optionally a $params parameter
-	 * specifying the values to be bound to the query.
-	 *
-	 * The $condition parameter should be either a string (e.g. 'id=1') or an array.
-	 * If the latter, it must be in one of the following two formats:
-	 *
-	 * - hash format: `array('column1' => value1, 'column2' => value2, ...)`
-	 * - operator format: `array(operator, operand1, operand2, ...)`
-	 *
-	 * A condition in hash format represents the following SQL expression in general:
-	 * `column1=value1 AND column2=value2 AND ...`. In case when a value is an array,
-	 * an `IN` expression will be generated. And if a value is null, `IS NULL` will be used
-	 * in the generated expression. Below are some examples:
-	 *
-	 * - `array('type'=>1, 'status'=>2)` generates `(type=1) AND (status=2)`.
-	 * - `array('id'=>array(1,2,3), 'status'=>2)` generates `(id IN (1,2,3)) AND (status=2)`.
-	 * - `array('status'=>null) generates `status IS NULL`.
-	 *
-	 * A condition in operator format generates the SQL expression according to the specified operator, which
-	 * can be one of the followings:
-	 *
-	 * - `and`: the operands should be concatenated together using `AND`. For example,
-	 * `array('and', 'id=1', 'id=2')` will generate `id=1 AND id=2`. If an operand is an array,
-	 * it will be converted into a string using the rules described here. For example,
-	 * `array('and', 'type=1', array('or', 'id=1', 'id=2'))` will generate `type=1 AND (id=1 OR id=2)`.
-	 * The method will NOT do any quoting or escaping.
-	 *
-	 * - `or`: similar to the `and` operator except that the operands are concatenated using `OR`.
-	 *
-	 * - `between`: operand 1 should be the column name, and operand 2 and 3 should be the
-	 * starting and ending values of the range that the column is in.
-	 * For example, `array('between', 'id', 1, 10)` will generate `id BETWEEN 1 AND 10`.
-	 *
-	 * - `not between`: similar to `between` except the `BETWEEN` is replaced with `NOT BETWEEN`
-	 * in the generated condition.
-	 *
-	 * - `in`: operand 1 should be a column or DB expression, and operand 2 be an array representing
-	 * the range of the values that the column or DB expression should be in. For example,
-	 * `array('in', 'id', array(1,2,3))` will generate `id IN (1,2,3)`.
-	 * The method will properly quote the column name and escape values in the range.
-	 *
-	 * - `not in`: similar to the `in` operator except that `IN` is replaced with `NOT IN` in the generated condition.
-	 *
-	 * - `like`: operand 1 should be a column or DB expression, and operand 2 be a string or an array representing
-	 * the values that the column or DB expression should be like.
-	 * For example, `array('like', 'name', '%tester%')` will generate `name LIKE '%tester%'`.
-	 * When the value range is given as an array, multiple `LIKE` predicates will be generated and concatenated
-	 * using `AND`. For example, `array('like', 'name', array('%test%', '%sample%'))` will generate
-	 * `name LIKE '%test%' AND name LIKE '%sample%'`.
-	 * The method will properly quote the column name and escape values in the range.
-	 *
-	 * - `or like`: similar to the `like` operator except that `OR` is used to concatenate the `LIKE`
-	 * predicates when operand 2 is an array.
-	 *
-	 * - `not like`: similar to the `like` operator except that `LIKE` is replaced with `NOT LIKE`
-	 * in the generated condition.
-	 *
-	 * - `or not like`: similar to the `not like` operator except that `OR` is used to concatenate
-	 * the `NOT LIKE` predicates.
-	 *
-	 * @param string|array $condition the conditions that should be put in the WHERE part.
-	 * @param array $params the parameters (name=>value) to be bound to the query.
-	 * For anonymous parameters, they can alternatively be specified as separate parameters to this method.
-	 * For example, `where('type=? AND status=?', 100, 1)`.
-	 * @return Query the query object itself
-	 * @see andWhere()
-	 * @see orWhere()
-	 */
-	public function where($condition, $params = array())
-	{
-		$this->where = $condition;
-		if (!is_array($params)) {
-			$params = func_get_args();
-			array_shift($params);
-		}
-		$this->addParams($params);
-		return $this;
-	}
-
-	/**
-	 * Adds an additional WHERE condition to the existing one.
-	 * The new condition and the existing one will be joined using the 'AND' operator.
-	 * @param string|array $condition the new WHERE condition. Please refer to [[where()]]
-	 * on how to specify this parameter.
-	 * @param array $params the parameters (name=>value) to be bound to the query.
-	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
-	 * @see where()
-	 * @see orWhere()
-	 */	
-	public function andWhere($condition, $params = array())
-	{
-		if ($this->where === null) {
-			$this->where = $condition;
-		} else {
-			$this->where = array('and', $this->where, $condition);
-		}
-		if (!is_array($params)) {
-			$params = func_get_args();
-			array_shift($params);
-		}
-		$this->addParams($params);
-		return $this;
-	}
-
-	/**
-	 * Adds an additional WHERE condition to the existing one.
-	 * The new condition and the existing one will be joined using the 'OR' operator.
-	 * @param string|array $condition the new WHERE condition. Please refer to [[where()]]
-	 * on how to specify this parameter.
-	 * @param array $params the parameters (name=>value) to be bound to the query.
-	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
-	 * @see where()
-	 * @see andWhere()
-	 */
-	public function orWhere($condition, $params = array())
-	{
-		if ($this->where === null) {
-			$this->where = $condition;
-		} else {
-			$this->where = array('or', $this->where, $condition);
-		}
-		if (!is_array($params)) {
-			$params = func_get_args();
-			array_shift($params);
-		}
-		$this->addParams($params);
-		return $this;
-	}
-
-	/**
-	 * Appends an INNER JOIN part to the query.
-	 * @param string $table the table to be joined.
-	 * Table name can contain schema prefix (e.g. 'public.tbl_user') and/or table alias (e.g. 'tbl_user u').
-	 * The method will automatically quote the table name unless it contains some parenthesis
-	 * (which means the table is given as a sub-query or DB expression).
-	 * @param string|array $condition the join condition that should appear in the ON part.
-	 * Please refer to [[where()]] on how to specify this parameter.
-	 * @param array $params the parameters (name=>value) to be bound to the query.
-	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
-	 */
-	public function join($table, $condition, $params = array())
-	{
-		$this->join[] = array('JOIN', $table, $condition);
-		if (!is_array($params)) {
-			$params = func_get_args();
-			array_shift($params);
-			array_shift($params);
-		}
-		return $this->addParams($params);
-	}
-
-	/**
-	 * Appends a LEFT OUTER JOIN part to the query.
-	 * @param string $table the table to be joined.
-	 * Table name can contain schema prefix (e.g. 'public.tbl_user') and/or table alias (e.g. 'tbl_user u').
-	 * The method will automatically quote the table name unless it contains some parenthesis
-	 * (which means the table is given as a sub-query or DB expression).
-	 * @param string|array $condition the join condition that should appear in the ON part.
-	 * Please refer to [[where()]] on how to specify this parameter.
-	 * @param array $params the parameters (name=>value) to be bound to the query
-	 * @return Query the query object itself
-	 */
-	public function leftJoin($table, $condition, $params = array())
-	{
-		$this->join[] = array('LEFT JOIN', $table, $condition);
-		if (!is_array($params)) {
-			$params = func_get_args();
-			array_shift($params);
-			array_shift($params);
-		}
-		return $this->addParams($params);
-	}
-
-	/**
-	 * Appends a RIGHT OUTER JOIN part to the query.
-	 * @param string $table the table to be joined.
-	 * Table name can contain schema prefix (e.g. 'public.tbl_user') and/or table alias (e.g. 'tbl_user u').
-	 * The method will automatically quote the table name unless it contains some parenthesis
-	 * (which means the table is given as a sub-query or DB expression).
-	 * @param string|array $condition the join condition that should appear in the ON part.
-	 * Please refer to [[where()]] on how to specify this parameter.
-	 * @param array $params the parameters (name=>value) to be bound to the query
-	 * @return Query the query object itself
-	 */
-	public function rightJoin($table, $condition, $params = array())
-	{
-		$this->join[] = array('RIGHT JOIN', $table, $condition);
-		if (!is_array($params)) {
-			$params = func_get_args();
-			array_shift($params);
-			array_shift($params);
-		}
-		return $this->addParams($params);
-	}
-
-	/**
-	 * Appends a CROSS JOIN part to the query.
-	 * Note that not all DBMS support CROSS JOIN.
-	 * @param string $table the table to be joined.
-	 * Table name can contain schema prefix (e.g. 'public.tbl_user') and/or table alias (e.g. 'tbl_user u').
-	 * The method will automatically quote the table name unless it contains some parenthesis
-	 * (which means the table is given as a sub-query or DB expression).
-	 * @return Query the query object itself
-	 */
-	public function crossJoin($table)
-	{
-		$this->join[] = array('CROSS JOIN', $table);
-		return $this;
-	}
-
-	/**
-	 * Appends a NATURAL JOIN part to the query.
-	 * Note that not all DBMS support NATURAL JOIN.
-	 * @param string $table the table to be joined.
-	 * Table name can contain schema prefix (e.g. 'public.tbl_user') and/or table alias (e.g. 'tbl_user u').
-	 * The method will automatically quote the table name unless it contains some parenthesis
-	 * (which means the table is given as a sub-query or DB expression).
-	 * @return Query the query object itself
-	 */
-	public function naturalJoin($table)
-	{
-		$this->join[] = array('NATURAL JOIN', $table);
-		return $this;
-	}
-
-	/**
-	 * Sets the GROUP BY part of the query.
-	 * @param string|array $columns the columns to be grouped by.
-	 * Columns can be specified in either a string (e.g. "id, name") or an array (e.g. array('id', 'name')).
-	 * The method will automatically quote the column names unless a column contains some parenthesis
-	 * (which means the column contains a DB expression).
-	 * @return Query the query object itself
-	 * @see addGroupBy()
-	 */
-	public function groupBy($columns)
-	{
-		$this->groupBy = $columns;
-		return $this;
-	}
-
-	/**
-	 * Adds additional group-by columns to the existing ones.
-	 * @param string|array $columns additional columns to be grouped by.
-	 * Columns can be specified in either a string (e.g. "id, name") or an array (e.g. array('id', 'name')).
-	 * The method will automatically quote the column names unless a column contains some parenthesis
-	 * (which means the column contains a DB expression).
-	 * @return Query the query object itself
-	 * @see groupBy()
-	 */
-	public function addGroupBy($columns)
-	{
-		if (empty($this->groupBy)) {
-			$this->groupBy = $columns;
-		} else {
-			if (!is_array($this->groupBy)) {
-				$this->groupBy = preg_split('/\s*,\s*/', trim($this->groupBy), -1, PREG_SPLIT_NO_EMPTY);
-			}
-			if (!is_array($columns)) {
-				$columns = preg_split('/\s*,\s*/', trim($columns), -1, PREG_SPLIT_NO_EMPTY);
-			}
-			$this->groupBy = array_merge($this->groupBy, $columns);
-		}
-		return $this;
-	}
 
 	/**
-	 * Sets the HAVING part of the query.
-	 * @param string|array $condition the conditions to be put after HAVING.
-	 * Please refer to [[where()]] on how to specify this parameter.
-	 * @param array $params the parameters (name=>value) to be bound to the query.
-	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
-	 * @see andHaving()
-	 * @see orHaving()
-	 */
-	public function having($condition, $params = array())
-	{
-		$this->having = $condition;
-		if (!is_array($params)) {
-			$params = func_get_args();
-			array_shift($params);
-		}
-		$this->addParams($params);
-		return $this;
-	}
-
-	/**
-	 * Adds an additional HAVING condition to the existing one.
-	 * The new condition and the existing one will be joined using the 'AND' operator.
-	 * @param string|array $condition the new HAVING condition. Please refer to [[where()]]
-	 * on how to specify this parameter.
-	 * @param array $params the parameters (name=>value) to be bound to the query.
-	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
-	 * @see having()
-	 * @see orHaving()
-	 */
-	public function andHaving($condition, $params = array())
-	{
-		if ($this->having === null) {
-			$this->having = $condition;
-		} else {
-			$this->having = array('and', $this->having, $condition);
-		}
-		if (!is_array($params)) {
-			$params = func_get_args();
-			array_shift($params);
-		}
-		$this->addParams($params);
-		return $this;
-	}
-
-	/**
-	 * Adds an additional HAVING condition to the existing one.
-	 * The new condition and the existing one will be joined using the 'OR' operator.
-	 * @param string|array $condition the new HAVING condition. Please refer to [[where()]]
-	 * on how to specify this parameter.
-	 * @param array $params the parameters (name=>value) to be bound to the query.
-	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
-	 * @see having()
-	 * @see andHaving()
-	 */
-	public function orHaving($condition, $params = array())
-	{
-		if ($this->having === null) {
-			$this->having = $condition;
-		} else {
-			$this->having = array('or', $this->having, $condition);
-		}
-		if (!is_array($params)) {
-			$params = func_get_args();
-			array_shift($params);
-		}
-		$this->addParams($params);
-		return $this;
-	}
-
-	/**
-	 * Sets the ORDER BY part of the query.
-	 * @param string|array $columns the columns (and the directions) to be ordered by.
-	 * Columns can be specified in either a string (e.g. "id ASC, name DESC") or an array (e.g. array('id ASC', 'name DESC')).
-	 * The method will automatically quote the column names unless a column contains some parenthesis
-	 * (which means the column contains a DB expression).
-	 * @return Query the query object itself
-	 * @see addOrderBy()
-	 */
-	public function orderBy($columns)
-	{
-		$this->orderBy = $columns;
-		return $this;
-	}
-
-	/**
-	 * Adds additional ORDER BY columns to the query.
-	 * @param string|array $columns the columns (and the directions) to be ordered by.
-	 * Columns can be specified in either a string (e.g. "id ASC, name DESC") or an array (e.g. array('id ASC', 'name DESC')).
-	 * The method will automatically quote the column names unless a column contains some parenthesis
-	 * (which means the column contains a DB expression).
-	 * @return Query the query object itself
-	 * @see orderBy()
-	 */
-	public function addOrderBy($columns)
-	{
-		if (empty($this->orderBy)) {
-			$this->orderBy = $columns;
-		} else {
-			if (!is_array($this->orderBy)) {
-				$this->orderBy = preg_split('/\s*,\s*/', trim($this->orderBy), -1, PREG_SPLIT_NO_EMPTY);
-			}
-			if (!is_array($columns)) {
-				$columns = preg_split('/\s*,\s*/', trim($columns), -1, PREG_SPLIT_NO_EMPTY);
-			}
-			$this->orderBy = array_merge($this->orderBy, $columns);
-		}
-		return $this;
-	}
-
-	/**
-	 * Sets the LIMIT part of the query.
-	 * @param integer $limit the limit
-	 * @return Query the query object itself
-	 */
-	public function limit($limit)
-	{
-		$this->limit = $limit;
-		return $this;
-	}
-
-	/**
-	 * Sets the OFFSET part of the query.
-	 * @param integer $offset the offset
-	 * @return Query the query object itself
-	 */
-	public function offset($offset)
-	{
-		$this->offset = $offset;
-		return $this;
-	}
-
-	/**
-	 * Appends a SQL statement using UNION operator.
-	 * @param string $sql the SQL statement to be appended using UNION
-	 * @return Query the query object itself
-	 */
-	public function union($sql)
-	{
-		$this->union[] = $sql;
-		return $this;
-	}
-
-	/**
-	 * Sets the parameters to be bound to the query.
-	 * @param array list of query parameter values indexed by parameter placeholders.
-	 * For example, `array(':name'=>'Dan', ':age'=>31)`.
-	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
-	 * @see addParams()
+	 * Generates and returns the SQL statement according to this query.
+	 * @param Connection $connection the database connection used to generate the SQL statement.
+	 * If this parameter is not given, the `db` application component will be used.
+	 * @return string the generated SQL statement
 	 */
-	public function params($params)
+	public function getSql($connection = null)
 	{
-		if (!is_array($params)) {
-			$params = func_get_args();
+		if ($connection === null) {
+			$connection = \Yii::$application->db;
 		}
-		$this->params = $params;
-		return $this;
+		return $connection->getQueryBuilder()->build($this);
 	}
 
 	/**
-	 * Adds additional parameters to be bound to the query.
-	 * @param array list of query parameter values indexed by parameter placeholders.
-	 * For example, `array(':name'=>'Dan', ':age'=>31)`.
-	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
-	 * @see params()
+	 * Creates a DB command that can be used to execute this query.
+	 * @param Connection $connection the database connection used to generate the SQL statement.
+	 * If this parameter is not given, the `db` application component will be used.
+	 * @return Command the created DB command instance.
 	 */
-	public function addParams($params)
+	public function createCommand($connection = null)
 	{
-		if (!is_array($params)) {
-			$params = func_get_args();
-		}
-		foreach ($params as $name => $value) {
-			if (is_integer($name)) {
-				$this->params[] = $value;
-			} else {
-				$this->params[$name] = $value;
-			}
+		if ($connection === null) {
+			$connection = \Yii::$application->db;
 		}
-		return $this;
+		return $connection->createCommand($this);
 	}
 
 	/**
@@ -643,7 +108,7 @@ class Query extends \yii\base\Object
 			$params = func_get_args();
 			array_shift($params);
 			array_shift($params);
-			array_shift($params);
+			unset($params[0]);
 		}
 		$this->addParams($params);
 		$this->operation = array(__FUNCTION__, $table, $columns, $condition, array());
@@ -664,7 +129,7 @@ class Query extends \yii\base\Object
 		if (!is_array($params)) {
 			$params = func_get_args();
 			array_shift($params);
-			array_shift($params);
+			unset($params[0]);
 		}
 		$this->operation = array(__FUNCTION__, $table, $condition);
 		return $this->addParams($params);
@@ -839,147 +304,4 @@ class Query extends \yii\base\Object
 		$this->operation = array(__FUNCTION__, $name, $table);
 		return $this;
 	}
-
-	/**
-	 * Generates and returns the SQL statement according to this query.
-	 * @param Connection $connection the database connection used to generate the SQL statement.
-	 * If this parameter is not given, the `db` application component will be used.
-	 * @return string the generated SQL statement
-	 */
-	public function getSql($connection = null)
-	{
-		if ($connection === null) {
-			$connection = \Yii::$application->db;
-		}
-		return $connection->getQueryBuilder()->build($this);
-	}
-
-	/**
-	 * Creates a DB command that can be used to execute this query.
-	 * @param Connection $connection the database connection used to generate the SQL statement.
-	 * If this parameter is not given, the `db` application component will be used.
-	 * @return Command the created DB command instance.
-	 */
-	public function createCommand($connection = null)
-	{
-		if ($connection === null) {
-			$connection = \Yii::$application->db;
-		}
-		return $connection->createCommand($this);
-	}
-
-	/**
-	 * Resets the query object to its original state.
-	 * @return Query the query object itself
-	 */
-	public function reset()
-	{
-		foreach (get_object_vars($this) as $name => $value) {
-			$this->$name = null;
-		}
-		return $this;
-	}
-
-	/**
-	 * Merges this query with another one.
-	 *
-	 * The merging is done according to the following rules:
-	 *
-	 * - [[select]]: the union of both queries' [[select]] property values.
-	 * - [[selectOption]], [[distinct]], [[limit]], [[offset]]: the new query
-	 * takes precedence over this query.
-	 *  - [[where]], [[having]]: the new query's corresponding property value
-	 * will be 'AND' together with the existing one.
-	 * - [[params]], [[orderBy]], [[groupBy]], [[join]], [[union]]: the new query's
-	 * corresponding property value will be appended to the existing one.
-	 *
-	 * In general, the merging makes the resulting query more restrictive and specific.
-	 * @param array|Query $query the new query to be merged with this query.
-	 * @return Query the query object itself
-	 */
-	public function mergeWith($query)
-	{
-		if (is_array($query)) {
-			$class = '\\' . get_class($this);
-			$query = $class::newInstance($query);
-		}
-
-		if ($this->select !== $query->select) {
-			if (empty($this->select)) {
-				$this->select = $query->select;
-			} elseif (!empty($query->select)) {
-				$select1 = is_string($this->select) ? preg_split('/\s*,\s*/', trim($this->select), -1, PREG_SPLIT_NO_EMPTY) : $this->select;
-				$select2 = is_string($query->select) ? preg_split('/\s*,\s*/', trim($query->select), -1, PREG_SPLIT_NO_EMPTY) : $query->select;
-				$this->select = array_merge($select1, array_diff($select2, $select1));
-			}
-		}
-
-		if ($query->selectOption !== null) {
-			$this->selectOption = $query->selectOption;
-		}
-
-		if ($query->distinct !== null) {
-			$this->distinct = $query->distinct;
-		}
-
-		if ($query->limit !== null) {
-			$this->limit = $query->limit;
-		}
-
-		if ($query->offset !== null) {
-			$this->offset = $query->offset;
-		}
-
-		if ($query->where !== null) {
-			$this->andWhere($query->where);
-		}
-
-		if ($query->having !== null) {
-			$this->andHaving($query->having);
-		}
-
-		if ($query->params !== null) {
-			$this->addParams($query->params);
-		}
-
-		if ($query->orderBy !== null) {
-			$this->addOrderBy($query->orderBy);
-		}
-
-		if ($query->groupBy !== null) {
-			$this->addGroupBy($query->groupBy);
-		}
-
-		if ($query->join !== null) {
-			if (empty($this->join)) {
-				$this->join = $query->join;
-			} else {
-				if (!is_array($this->join)) {
-					$this->join = array($this->join);
-				}
-				if (is_array($query->join)) {
-					$this->join = array_merge($this->join, $query->join);
-				} else {
-					$this->join[] = $query->join;
-				}
-			}
-		}
-
-		if ($query->union !== null) {
-			if (empty($this->union)) {
-				$this->union = $query->union;
-			} else {
-				if (!is_array($this->union)) {
-					$this->union = array($this->union);
-				}
-				if (is_array($query->union)) {
-					$this->union = array_merge($this->union, $query->union);
-				} else {
-					$this->union[] = $query->union;
-				}
-			}
-		}
-
-		return $this;
-	}
 }
diff --git a/framework/util/Text.php b/framework/util/Text.php
index c41a6e2..7ff7555 100644
--- a/framework/util/Text.php
+++ b/framework/util/Text.php
@@ -44,8 +44,27 @@ class Text
 		return $name . 's';
 	}
 
-	public static function dd($value)
+	/**
+	 * Converts a class name into space-separated words.
+	 * For example, 'PostTag' will be converted as 'Post Tag'.
+	 * @param string $name the string to be converted
+	 * @param boolean $ucwords whether to capitalize the first letter in each word
+	 * @return string the resulting words
+	 */
+	public static function name2words($name, $ucwords = true)
+	{
+		$label = trim(strtolower(str_replace(array('-', '_', '.'), ' ', preg_replace('/(?<![A-Z])[A-Z]/', ' \0', $name))));
+		return $ucwords ? ucwords($label) : $label;
+	}
+
+	/**
+	 * Converts a class name into a HTML ID.
+	 * For example, 'PostTag' will be converted as 'post-tag'.
+	 * @param string $name the string to be converted
+	 * @return string the resulting ID
+	 */
+	public static function name2id($name)
 	{
-		return trim(strtolower(str_replace(array('-', '_', '.'), ' ', preg_replace('/(?<![A-Z])[A-Z]/', ' \0', $value))));
+		return trim(strtolower(str_replace('_','-',preg_replace('/(?<![A-Z])[A-Z]/', '-\0', $name))),'-');
 	}
 }
diff --git a/tests/unit/framework/base/BehaviorTest.php b/tests/unit/framework/base/BehaviorTest.php
index 4d66bdc..009d859 100644
--- a/tests/unit/framework/base/BehaviorTest.php
+++ b/tests/unit/framework/base/BehaviorTest.php
@@ -7,6 +7,16 @@ class BarClass extends \yii\base\Component
 
 }
 
+class FooClass extends \yii\base\Component
+{
+	public function behaviors()
+	{
+		return array(
+			'foo' => __NAMESPACE__ . '\BarBehavior',
+		);
+	}
+}
+
 class BarBehavior extends \yii\base\Behavior
 {
 	public $behaviorProperty = 'behavior property';
@@ -21,12 +31,19 @@ class BehaviorTest extends \yiiunit\TestCase
 {
 	public function testAttachAndAccessing()
 	{
-		$bar = BarClass::newInstance();
+		$bar = new BarClass();
 		$behavior = new BarBehavior();
 		$bar->attachBehavior('bar', $behavior);
 		$this->assertEquals('behavior property', $bar->behaviorProperty);
 		$this->assertEquals('behavior method', $bar->behaviorMethod());
-		$this->assertEquals('behavior property', $bar->bar->behaviorProperty);
-		$this->assertEquals('behavior method', $bar->bar->behaviorMethod());
+		$this->assertEquals('behavior property', $bar->asa('bar')->behaviorProperty);
+		$this->assertEquals('behavior method', $bar->asa('bar')->behaviorMethod());
+	}
+
+	public function testAutomaticAttach()
+	{
+		$foo = new FooClass();
+		$this->assertEquals('behavior property', $foo->behaviorProperty);
+		$this->assertEquals('behavior method', $foo->behaviorMethod());
 	}
 }