diff --git a/framework/CHANGELOG.md b/framework/CHANGELOG.md
index cf6eb5a..fb51798 100644
--- a/framework/CHANGELOG.md
+++ b/framework/CHANGELOG.md
@@ -16,6 +16,7 @@ Yii Framework 2 Change Log
 - Bug: Fixed incorrect event name for `yii\jui\Spinner` (samdark)
 - Bug: Json::encode() did not handle objects that implement JsonSerializable interface correctly (cebe)
 - Bug: Fixed issue with tabular input on ActiveField::radio() and ActiveField::checkbox() (jom)
+- Enh #797: Added support for validating multiple columns by `UniqueValidator` and `ExistValidator` (qiangxue)
 - Enh #1293: Replaced Console::showProgress() with a better approach. See Console::startProgress() for details (cebe)
 - Enh #1406: DB Schema support for Oracle Database (p0larbeer, qiangxue)
 - Enh #1437: Added ListView::viewParams (qiangxue)
diff --git a/framework/yii/validators/ExistValidator.php b/framework/yii/validators/ExistValidator.php
index 04d8af8..c205655 100644
--- a/framework/yii/validators/ExistValidator.php
+++ b/framework/yii/validators/ExistValidator.php
@@ -30,10 +30,25 @@ class ExistValidator extends Validator
 	 */
 	public $className;
 	/**
-	 * @var string the yii\db\ActiveRecord class attribute name that should be
+	 * @var string|array the ActiveRecord class attribute name that should be
 	 * used to look for the attribute value being validated. Defaults to null,
-	 * meaning using the name of the attribute being validated.
-	 * @see className
+	 * meaning using the name of the attribute being validated. Use a string
+	 * to specify the attribute that is different from the attribute being validated
+	 * (often used together with [[className]]). Use an array to validate the existence about
+	 * multiple columns. For example,
+	 *
+	 * ```php
+	 * // a1 needs to exist
+	 * array('a1', 'exist')
+	 * // a1 needs to exist, but its value will use a2 to check for the existence
+	 * array('a1', 'exist', 'attributeName' => 'a2')
+	 * // a1 and a2 need to exist together, and they both will receive error message
+	 * array('a1, a2', 'exist', 'attributeName' => array('a1', 'a2'))
+	 * // a1 and a2 need to exist together, only a1 will receive error message
+	 * array('a1', 'exist', 'attributeName' => array('a1', 'a2'))
+	 * // a1 and a2 need to exist together, a2 will take value 10, only a1 will receive error message
+	 * array('a1', 'exist', 'attributeName' => array('a1', 'a2' => 10))
+	 * ```
 	 */
 	public $attributeName;
 
@@ -64,9 +79,7 @@ class ExistValidator extends Validator
 		/** @var \yii\db\ActiveRecordInterface $className */
 		$className = $this->className === null ? get_class($object) : $this->className;
 		$attributeName = $this->attributeName === null ? $attribute : $this->attributeName;
-		$query = $className::find();
-		$query->where([$attributeName => $value]);
-		if (!$query->exists()) {
+		if (!$this->exists($className, $attributeName, $object, $value)) {
 			$this->addError($object, $attribute, $this->message);
 		}
 	}
@@ -85,10 +98,33 @@ class ExistValidator extends Validator
 		if ($this->attributeName === null) {
 			throw new InvalidConfigException('The "attributeName" property must be set.');
 		}
+		return $this->exists($this->className, $this->attributeName, null, $value) ? null : [$this->message, []];
+	}
+
+	/**
+	 * Performs existence check.
+	 * @param string $className the AR class name to be checked against
+	 * @param string|array $attributeName the attribute(s) to be checked
+	 * @param \yii\db\ActiveRecordInterface $object the object whose value is being validated
+	 * @param mixed $value the attribute value currently being validated
+	 * @return boolean whether the data being validated exists in the database already
+	 */
+	protected function exists($className, $attributeName, $object, $value)
+	{
 		/** @var \yii\db\ActiveRecordInterface $className */
-		$className = $this->className;
 		$query = $className::find();
-		$query->where([$this->attributeName => $value]);
-		return $query->exists() ? null : [$this->message, []];
+		if (is_array($attributeName)) {
+			$params = [];
+			foreach ($attributeName as $k => $v) {
+				if (is_integer($k)) {
+					$params[$v] = $this->className === null && $object !== null ? $object->$v : $value;
+				} else {
+					$params[$k] = $v;
+				}
+			}
+		} else {
+			$params = [$attributeName => $value];
+		}
+		return $query->where($params)->exists();
 	}
 }
diff --git a/framework/yii/validators/UniqueValidator.php b/framework/yii/validators/UniqueValidator.php
index 53b6739..a497ead 100644
--- a/framework/yii/validators/UniqueValidator.php
+++ b/framework/yii/validators/UniqueValidator.php
@@ -26,9 +26,25 @@ class UniqueValidator extends Validator
 	 */
 	public $className;
 	/**
-	 * @var string the ActiveRecord class attribute name that should be
+	 * @var string|array the ActiveRecord class attribute name that should be
 	 * used to look for the attribute value being validated. Defaults to null,
-	 * meaning using the name of the attribute being validated.
+	 * meaning using the name of the attribute being validated. Use a string
+	 * to specify the attribute that is different from the attribute being validated
+	 * (often used together with [[className]]). Use an array to validate uniqueness about
+	 * multiple columns. For example,
+	 *
+	 * ```php
+	 * // a1 needs to be unique
+	 * array('a1', 'unique')
+	 * // a1 needs to be unique, but its value will use a2 to check for the uniqueness
+	 * array('a1', 'unique', 'attributeName' => 'a2')
+	 * // a1 and a2 need to unique together, and they both will receive error message
+	 * array('a1, a2', 'unique', 'attributeName' => array('a1', 'a2'))
+	 * // a1 and a2 need to unique together, only a1 will receive error message
+	 * array('a1', 'unique', 'attributeName' => array('a1', 'a2'))
+	 * // a1 and a2 need to unique together, a2 will take value 10, only a1 will receive error message
+	 * array('a1', 'unique', 'attributeName' => array('a1', 'a2' => 10))
+	 * ```
 	 */
 	public $attributeName;
 
@@ -60,7 +76,20 @@ class UniqueValidator extends Validator
 		$attributeName = $this->attributeName === null ? $attribute : $this->attributeName;
 
 		$query = $className::find();
-		$query->where([$attributeName => $value]);
+
+		if (is_array($attributeName)) {
+			$params = [];
+			foreach ($attributeName as $k => $v) {
+				if (is_integer($k)) {
+					$params[$v] = $this->className === null ? $object->$v : $value;
+				} else {
+					$params[$k] = $v;
+				}
+			}
+		} else {
+			$params = [$attributeName => $value];
+		}
+		$query->where($params);
 
 		if (!$object instanceof ActiveRecordInterface || $object->getIsNewRecord()) {
 			// if current $object isn't in the database yet then it's OK just to call exists()
@@ -71,7 +100,11 @@ class UniqueValidator extends Validator
 			$objects = $query->limit(2)->all();
 			$n = count($objects);
 			if ($n === 1) {
-				if (in_array($attributeName, $className::primaryKey())) {
+				$keys = array_keys($params);
+				$pks = $className::primaryKey();
+				sort($keys);
+				sort($pks);
+				if ($keys === $pks) {
 					// primary key is modified and not unique
 					$exists = $object->getOldPrimaryKey() != $object->getPrimaryKey();
 				} else {
diff --git a/tests/unit/framework/validators/ExistValidatorTest.php b/tests/unit/framework/validators/ExistValidatorTest.php
index 45ff5d5..03332ad 100644
--- a/tests/unit/framework/validators/ExistValidatorTest.php
+++ b/tests/unit/framework/validators/ExistValidatorTest.php
@@ -7,6 +7,8 @@ use Yii;
 use yii\base\Exception;
 use yii\validators\ExistValidator;
 use yiiunit\data\ar\ActiveRecord;
+use yiiunit\data\ar\Order;
+use yiiunit\data\ar\OrderItem;
 use yiiunit\data\validators\models\ValidatorTestMainModel;
 use yiiunit\data\validators\models\ValidatorTestRefModel;
 use yiiunit\framework\db\DatabaseTestCase;
@@ -92,4 +94,44 @@ class ExistValidatorTest extends DatabaseTestCase
 		$val->validateAttribute($m, 'test_val');
 		$this->assertTrue($m->hasErrors('test_val'));
 	}
+
+	public function testValidateCompositeKeys()
+	{
+		$val = new ExistValidator([
+			'className' => OrderItem::className(),
+			'attributeName' => ['order_id', 'item_id'],
+		]);
+		// validate old record
+		$m = OrderItem::find(['order_id' => 1, 'item_id' => 2]);
+		$val->validateAttribute($m, 'order_id');
+		$this->assertFalse($m->hasErrors('order_id'));
+
+		// validate new record
+		$m = new OrderItem(['order_id' => 1, 'item_id' => 2]);
+		$val->validateAttribute($m, 'order_id');
+		$this->assertFalse($m->hasErrors('order_id'));
+		$m = new OrderItem(['order_id' => 10, 'item_id' => 2]);
+		$val->validateAttribute($m, 'order_id');
+		$this->assertTrue($m->hasErrors('order_id'));
+
+		$val = new ExistValidator([
+			'className' => OrderItem::className(),
+			'attributeName' => ['order_id', 'item_id' => 2],
+		]);
+		// validate old record
+		$m = Order::find(1);
+		$val->validateAttribute($m, 'id');
+		$this->assertFalse($m->hasErrors('id'));
+		$m = Order::find(1);
+		$m->id = 10;
+		$val->validateAttribute($m, 'id');
+		$this->assertTrue($m->hasErrors('id'));
+
+		$m = new Order(['id' => 1]);
+		$val->validateAttribute($m, 'id');
+		$this->assertFalse($m->hasErrors('id'));
+		$m = new Order(['id' => 10]);
+		$val->validateAttribute($m, 'id');
+		$this->assertTrue($m->hasErrors('id'));
+	}
 }
diff --git a/tests/unit/framework/validators/UniqueValidatorTest.php b/tests/unit/framework/validators/UniqueValidatorTest.php
index 707239c..1631243 100644
--- a/tests/unit/framework/validators/UniqueValidatorTest.php
+++ b/tests/unit/framework/validators/UniqueValidatorTest.php
@@ -6,6 +6,8 @@ namespace yiiunit\framework\validators;
 use yii\validators\UniqueValidator;
 use Yii;
 use yiiunit\data\ar\ActiveRecord;
+use yiiunit\data\ar\Order;
+use yiiunit\data\ar\OrderItem;
 use yiiunit\data\validators\models\FakedValidationModel;
 use yiiunit\data\validators\models\ValidatorTestMainModel;
 use yiiunit\data\validators\models\ValidatorTestRefModel;
@@ -85,4 +87,49 @@ class UniqueValidatorTest extends DatabaseTestCase
 		$m = new ValidatorTestMainModel();
 		$val->validateAttribute($m, 'testMainVal');
 	}
+
+	public function testValidateCompositeKeys()
+	{
+		$val = new UniqueValidator([
+			'className' => OrderItem::className(),
+			'attributeName' => ['order_id', 'item_id'],
+		]);
+		// validate old record
+		$m = OrderItem::find(['order_id' => 1, 'item_id' => 2]);
+		$val->validateAttribute($m, 'order_id');
+		$this->assertFalse($m->hasErrors('order_id'));
+		$m->item_id = 1;
+		$val->validateAttribute($m, 'order_id');
+		$this->assertTrue($m->hasErrors('order_id'));
+
+		// validate new record
+		$m = new OrderItem(['order_id' => 1, 'item_id' => 2]);
+		$val->validateAttribute($m, 'order_id');
+		$this->assertTrue($m->hasErrors('order_id'));
+		$m = new OrderItem(['order_id' => 10, 'item_id' => 2]);
+		$val->validateAttribute($m, 'order_id');
+		$this->assertFalse($m->hasErrors('order_id'));
+
+		$val = new UniqueValidator([
+			'className' => OrderItem::className(),
+			'attributeName' => ['order_id', 'item_id' => 2],
+		]);
+		// validate old record
+		$m = Order::find(1);
+		$val->validateAttribute($m, 'id');
+		$this->assertFalse($m->hasErrors('id'));
+		$m->id = 2;
+		$val->validateAttribute($m, 'id');
+		$this->assertFalse($m->hasErrors('id'));
+		$m->id = 3;
+		$val->validateAttribute($m, 'id');
+		$this->assertTrue($m->hasErrors('id'));
+
+		$m = new Order(['id' => 1]);
+		$val->validateAttribute($m, 'id');
+		$this->assertTrue($m->hasErrors('id'));
+		$m = new Order(['id' => 10]);
+		$val->validateAttribute($m, 'id');
+		$this->assertFalse($m->hasErrors('id'));
+	}
 }