CMysqlSchema

public function addPrimaryKey($name,$table,$columns)
{
    if(is_string($columns))
        $columns=preg_split('/\s*,\s*/',$columns,-1,PREG_SPLIT_NO_EMPTY);
    foreach($columns as $i=>$col)
        $columns[$i]=$this->quoteColumnName($col);
    return 'ALTER TABLE ' . $this->quoteTableName($table) . ' ADD PRIMARY KEY ('
        . implode(', ', $columns). ' )';
}

public function checkIntegrity($check=true,$schema='')
{
    $this->getDbConnection()->createCommand('SET FOREIGN_KEY_CHECKS='.($check?1:0))->execute();
}

public function compareTableNames($name1,$name2)
{
    return parent::compareTableNames(strtolower($name1),strtolower($name2));
}

protected function createColumn($column)
{
    $c=new CMysqlColumnSchema;
    $c->name=$column['Field'];
    $c->rawName=$this->quoteColumnName($c->name);
    $c->allowNull=$column['Null']==='YES';
    $c->isPrimaryKey=strpos($column['Key'],'PRI')!==false;
    $c->isForeignKey=false;
    $c->init($column['Type'],$column['Default']);
    $c->autoIncrement=strpos(strtolower($column['Extra']),'auto_increment')!==false;
    if(isset($column['Comment']))
        $c->comment=$column['Comment'];

    return $c;
}

protected function createCommandBuilder()
{
    return new CMysqlCommandBuilder($this);
}

public function dropForeignKey($name, $table)
{
    return 'ALTER TABLE '.$this->quoteTableName($table)
        .' DROP FOREIGN KEY '.$this->quoteColumnName($name);
}

public function dropPrimaryKey($name,$table)
{
    return 'ALTER TABLE ' . $this->quoteTableName($table) . ' DROP PRIMARY KEY';

}

protected function findColumns($table)
{
    $sql='SHOW FULL COLUMNS FROM '.$table->rawName;
    try
    {
        $columns=$this->getDbConnection()->createCommand($sql)->queryAll();
    }
    catch(Exception $e)
    {
        return false;
    }
    foreach($columns as $column)
    {
        $c=$this->createColumn($column);
        $table->columns[$c->name]=$c;
        if($c->isPrimaryKey)
        {
            if($table->primaryKey===null)
                $table->primaryKey=$c->name;
            elseif(is_string($table->primaryKey))
                $table->primaryKey=array($table->primaryKey,$c->name);
            else
                $table->primaryKey[]=$c->name;
            if($c->autoIncrement)
                $table->sequenceName='';
        }
    }
    return true;
}

protected function findConstraints($table)
{
    $row=$this->getDbConnection()->createCommand('SHOW CREATE TABLE '.$table->rawName)->queryRow();
    $matches=array();
    $regexp='/FOREIGN KEY\s+\(([^\)]+)\)\s+REFERENCES\s+([^\(^\s]+)\s*\(([^\)]+)\)/mi';
    foreach($row as $sql)
    {
        if(preg_match_all($regexp,$sql,$matches,PREG_SET_ORDER))
            break;
    }
    foreach($matches as $match)
    {
        $keys=array_map('trim',explode(',',str_replace(array('`','"'),'',$match[1])));
        $fks=array_map('trim',explode(',',str_replace(array('`','"'),'',$match[3])));
        foreach($keys as $k=>$name)
        {
            $table->foreignKeys[$name]=array(str_replace(array('`','"'),'',$match[2]),$fks[$k]);
            if(isset($table->columns[$name]))
                $table->columns[$name]->isForeignKey=true;
        }
    }
}

protected function findTableNames($schema='')
{
    if($schema==='')
        return $this->getDbConnection()->createCommand('SHOW TABLES')->queryColumn();
    $names=$this->getDbConnection()->createCommand('SHOW TABLES FROM '.$this->quoteTableName($schema))->queryColumn();
    foreach($names as &$name)
        $name=$schema.'.'.$name;
    return $names;
}

protected function getServerVersion()
{
    $version=$this->getDbConnection()->getAttribute(PDO::ATTR_SERVER_VERSION);
    $digits=array();
    preg_match('/(\d+)\.(\d+)\.(\d+)/', $version, $digits);
    return floatval($digits[1].'.'.$digits[2].$digits[3]);
}

protected function loadTable($name)
{
    $table=new CMysqlTableSchema;
    $this->resolveTableNames($table,$name);

    if($this->findColumns($table))
    {
        $this->findConstraints($table);
        return $table;
    }
    else
        return null;
}

public function quoteSimpleColumnName($name)
{
    return '`'.$name.'`';
}

public function quoteSimpleTableName($name)
{
    return '`'.$name.'`';
}

public function renameColumn($table, $name, $newName)
{
    $db=$this->getDbConnection();
    $row=$db->createCommand('SHOW CREATE TABLE '.$db->quoteTableName($table))->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']))
        $sql=$row['Create Table'];
    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];
            }
        }
    }

    // try to give back a SQL anyway
    return "ALTER TABLE ".$db->quoteTableName($table)
        . " CHANGE ".$db->quoteColumnName($name).' '.$newName;
}

public function resetSequence($table,$value=null)
{
    if($table->sequenceName===null)
        return;
    if($value!==null)
        $value=(int)$value;
    else
    {
        $value=(int)$this->getDbConnection()
            ->createCommand("SELECT MAX(`{$table->primaryKey}`) FROM {$table->rawName}")
            ->queryScalar();
        $value++;
    }
    $this->getDbConnection()
        ->createCommand("ALTER TABLE {$table->rawName} AUTO_INCREMENT=$value")
        ->execute();
}

protected function resolveTableNames($table,$name)
{
    $parts=explode('.',str_replace(array('`','"'),'',$name));
    if(isset($parts[1]))
    {
        $table->schemaName=$parts[0];
        $table->name=$parts[1];
        $table->rawName=$this->quoteTableName($table->schemaName).'.'.$this->quoteTableName($table->name);
    }
    else
    {
        $table->name=$parts[0];
        $table->rawName=$this->quoteTableName($table->name);
    }
}