diff --git a/framework/db/dao/QueryBuilder.php b/framework/db/dao/QueryBuilder.php
index f26118b..fbbc05e 100644
--- a/framework/db/dao/QueryBuilder.php
+++ b/framework/db/dao/QueryBuilder.php
@@ -21,7 +21,7 @@ class QueryBuilder extends \yii\base\Component
 	/**
 	 * @var array the abstract column types mapped to physical column types.
 	 */
-    public $columnTypes = array(
+    public $typeMap = array(
         'pk' => 'int(11) NOT NULL AUTO_INCREMENT PRIMARY KEY',
         'string' => 'varchar(255)',
         'text' => 'text',
@@ -379,7 +379,7 @@ class QueryBuilder extends \yii\base\Component
 
 	/**
 	 * Converts an abstract column type into a physical column type.
-	 * The conversion is done using the type map specified in {@link columnTypes}.
+	 * The conversion is done using the type map specified in {@link typeMap}.
 	 * These abstract column types are supported (using MySQL as example to explain the corresponding
 	 * physical types):
 	 * <ul>
@@ -405,12 +405,12 @@ class QueryBuilder extends \yii\base\Component
 	 */
     public function getColumnType($type)
     {
-		if (isset($this->columnTypes[$type])) {
-			return $this->columnTypes[$type];
+		if (isset($this->typeMap[$type])) {
+			return $this->typeMap[$type];
 		}
 		elseif (($pos = strpos($type, ' ')) !== false) {
 			$t = substr($type, 0, $pos);
-			return (isset($this->columnTypes[$t]) ? $this->columnTypes[$t] : $t) . substr($type, $pos);
+			return (isset($this->typeMap[$t]) ? $this->typeMap[$t] : $t) . substr($type, $pos);
 		}
 		else {
 			return $type;
diff --git a/framework/db/dao/mysql/QueryBuilder.php b/framework/db/dao/mysql/QueryBuilder.php
index 9ec5842..497f457 100644
--- a/framework/db/dao/mysql/QueryBuilder.php
+++ b/framework/db/dao/mysql/QueryBuilder.php
@@ -49,33 +49,27 @@ class QueryBuilder extends \yii\db\dao\QueryBuilder
 	 */
 	public function renameColumn($table, $name, $newName)
 	{
-		$db = $this->getDbConnection();
-		$row = $db->createCommand('SHOW CREATE TABLE ' . $db->quoteTableName($table))->queryRow();
+		$quotedTable = $this->schema->quoteTableName($table);
+		$row = $this->connection->createCommand('SHOW CREATE TABLE ' . $quotedTable)->queryRow();
 		if ($row === false)
 			throw new CDbException(Yii::t('yii', 'Unable to find "{column}" in table "{table}".', array('{column}' => $name, '{table}' => $table)));
-		if (isset($row['Create Table']))
+		if (isset($row['Create Table'])) {
 			$sql = $row['Create Table'];
-		else
-		{
+		}
+		else {
 			$row = array_values($row);
 			$sql = $row[1];
 		}
-		if (preg_match_all('/^\s*`(.*?)`\s+(.*?),?$/m', $sql, $matches))
-		{
-			foreach ($matches[1] as $i => $c)
-			{
-				if ($c === $name)
-				{
-					return "ALTER TABLE " . $db->quoteTableName($table)
-						. " CHANGE " . $db->quoteColumnName($name)
-						. ' ' . $db->quoteColumnName($newName) . ' ' . $matches[2][$i];
+		if (preg_match_all('/^\s*`(.*?)`\s+(.*?),?$/m', $sql, $matches)) {
+			foreach ($matches[1] as $i => $c) {
+				if ($c === $name) {
+					return "ALTER TABLE $quotedTable CHANGE " . $this->schema->quoteColumnName($name)
+						. ' ' . $this->schema->quoteColumnName($newName) . ' ' . $matches[2][$i];
 				}
 			}
 		}
-
 		// try to give back a SQL anyway
-		return "ALTER TABLE " . $db->quoteTableName($table)
-			. " CHANGE " . $db->quoteColumnName($name) . ' ' . $newName;
+		return "ALTER TABLE $quotedTable CHANGE " . $this->schema->quoteColumnName($name) . ' ' . $newName;
 	}
 
 	/**
@@ -87,7 +81,7 @@ class QueryBuilder extends \yii\db\dao\QueryBuilder
 	 */
 	public function dropForeignKey($name, $table)
 	{
-		return 'ALTER TABLE ' . $this->quoteTableName($table)
-			. ' DROP FOREIGN KEY ' . $this->quoteColumnName($name);
+		return 'ALTER TABLE ' . $this->schema->quoteTableName($table)
+			. ' DROP FOREIGN KEY ' . $this->schema->quoteColumnName($name);
 	}
 }