CDbSchema

public function __construct($conn)
{
    $this->_connection=$conn;
    foreach($conn->schemaCachingExclude as $name)
        $this->_cacheExclude[$name]=true;
}

public function addColumn($table, $column, $type)
{
    return 'ALTER TABLE ' . $this->quoteTableName($table)
        . ' ADD ' . $this->quoteColumnName($column) . ' '
        . $this->getColumnType($type);
}

public function addForeignKey($name, $table, $columns, $refTable, $refColumns, $delete=null, $update=null)
{
    $columns=preg_split('/\s*,\s*/',$columns,-1,PREG_SPLIT_NO_EMPTY);
    foreach($columns as $i=>$col)
        $columns[$i]=$this->quoteColumnName($col);
    $refColumns=preg_split('/\s*,\s*/',$refColumns,-1,PREG_SPLIT_NO_EMPTY);
    foreach($refColumns as $i=>$col)
        $refColumns[$i]=$this->quoteColumnName($col);
    $sql='ALTER TABLE '.$this->quoteTableName($table)
        .' ADD CONSTRAINT '.$this->quoteColumnName($name)
        .' FOREIGN KEY ('.implode(', ', $columns).')'
        .' REFERENCES '.$this->quoteTableName($refTable)
        .' ('.implode(', ', $refColumns).')';
    if($delete!==null)
        $sql.=' ON DELETE '.$delete;
    if($update!==null)
        $sql.=' ON UPDATE '.$update;
    return $sql;
}

public function alterColumn($table, $column, $type)
{
    return 'ALTER TABLE ' . $this->quoteTableName($table) . ' CHANGE '
        . $this->quoteColumnName($column) . ' '
        . $this->quoteColumnName($column) . ' '
        . $this->getColumnType($type);
}

public function checkIntegrity($check=true,$schema='')
{
}

public function compareTableNames($name1,$name2)
{
    $name1=str_replace(array('"','`',"'"),'',$name1);
    $name2=str_replace(array('"','`',"'"),'',$name2);
    if(($pos=strrpos($name1,'.'))!==false)
        $name1=substr($name1,$pos+1);
    if(($pos=strrpos($name2,'.'))!==false)
        $name2=substr($name2,$pos+1);
    if($this->_connection->tablePrefix!==null)
    {
        if(strpos($name1,'{')!==false)
            $name1=$this->_connection->tablePrefix.str_replace(array('{','}'),'',$name1);
        if(strpos($name2,'{')!==false)
            $name2=$this->_connection->tablePrefix.str_replace(array('{','}'),'',$name2);
    }
    return $name1===$name2;
}

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

public function createIndex($name, $table, $column, $unique=false)
{
    $cols=array();
    $columns=preg_split('/\s*,\s*/',$column,-1,PREG_SPLIT_NO_EMPTY);
    foreach($columns as $col)
    {
        if(strpos($col,'(')!==false)
            $cols[]=$col;
        else
            $cols[]=$this->quoteColumnName($col);
    }
    return ($unique ? 'CREATE UNIQUE INDEX ' : 'CREATE INDEX ')
        . $this->quoteTableName($name).' ON '
        . $this->quoteTableName($table).' ('.implode(', ',$cols).')';
}

public function createTable($table, $columns, $options=null)
{
    $cols=array();
    foreach($columns as $name=>$type)
    {
        if(is_string($name))
            $cols[]="\t".$this->quoteColumnName($name).' '.$this->getColumnType($type);
        else
            $cols[]="\t".$type;
    }
    $sql="CREATE TABLE ".$this->quoteTableName($table)." (\n".implode(",\n",$cols)."\n)";
    return $options===null ? $sql : $sql.' '.$options;
}

public function dropColumn($table, $column)
{
    return "ALTER TABLE ".$this->quoteTableName($table)
        ." DROP COLUMN ".$this->quoteColumnName($column);
}

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

public function dropIndex($name, $table)
{
    return 'DROP INDEX '.$this->quoteTableName($name).' ON '.$this->quoteTableName($table);
}

public function dropTable($table)
{
    return "DROP TABLE ".$this->quoteTableName($table);
}

protected function findTableNames($schema='')
{
    throw new CDbException(Yii::t('yii','{class} does not support fetching all table names.',
        array('{class}'=>get_class($this))));
}

public function getColumnType($type)
{
    if(isset($this->columnTypes[$type]))
        return $this->columnTypes[$type];
    else if(($pos=strpos($type,' '))!==false)
    {
        $t=substr($type,0,$pos);
        return (isset($this->columnTypes[$t]) ? $this->columnTypes[$t] : $t).substr($type,$pos);
    }
    else
        return $type;
}

public function getCommandBuilder()
{
    if($this->_builder!==null)
        return $this->_builder;
    else
        return $this->_builder=$this->createCommandBuilder();
}

public function getDbConnection()
{
    return $this->_connection;
}

public function getTable($name,$refresh=false)
{
    if($refresh===false && isset($this->_tables[$name]))
        return $this->_tables[$name];
    else
    {
        if($this->_connection->tablePrefix!==null && strpos($name,'{{')!==false)
            $realName=preg_replace('/\{\{(.*?)\}\}/',$this->_connection->tablePrefix.'$1',$name);
        else
            $realName=$name;

        // temporarily disable query caching
        if($this->_connection->queryCachingDuration>0)
        {
            $qcDuration=$this->_connection->queryCachingDuration;
            $this->_connection->queryCachingDuration=0;
        }

        if(!isset($this->_cacheExclude[$name]) && ($duration=$this->_connection->schemaCachingDuration)>0 && $this->_connection->schemaCacheID!==false && ($cache=Yii::app()->getComponent($this->_connection->schemaCacheID))!==null)
        {
            $key='yii:dbschema'.$this->_connection->connectionString.':'.$this->_connection->username.':'.$name;
            $table=$cache->get($key);
            if($refresh===true || $table===false)
            {
                $table=$this->loadTable($realName);
                if($table!==null)
                    $cache->set($key,$table,$duration);
            }
            $this->_tables[$name]=$table;
        }
        else
            $this->_tables[$name]=$table=$this->loadTable($realName);

        if(isset($qcDuration))  // re-enable query caching
            $this->_connection->queryCachingDuration=$qcDuration;

        return $table;
    }
}

public function getTableNames($schema='')
{
    if(!isset($this->_tableNames[$schema]))
        $this->_tableNames[$schema]=$this->findTableNames($schema);
    return $this->_tableNames[$schema];
}

public function getTables($schema='')
{
    $tables=array();
    foreach($this->getTableNames($schema) as $name)
    {
        if(($table=$this->getTable($name))!==null)
            $tables[$name]=$table;
    }
    return $tables;
}

abstract protected function loadTable($name);

public function quoteColumnName($name)
{
    if(($pos=strrpos($name,'.'))!==false)
    {
        $prefix=$this->quoteTableName(substr($name,0,$pos)).'.';
        $name=substr($name,$pos+1);
    }
    else
        $prefix='';
    return $prefix . ($name==='*' ? $name : $this->quoteSimpleColumnName($name));
}

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

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

public function quoteTableName($name)
{
    if(strpos($name,'.')===false)
        return $this->quoteSimpleTableName($name);
    $parts=explode('.',$name);
    foreach($parts as $i=>$part)
        $parts[$i]=$this->quoteSimpleTableName($part);
    return implode('.',$parts);

}

public function refresh()
{
    if(($duration=$this->_connection->schemaCachingDuration)>0 && $this->_connection->schemaCacheID!==false && ($cache=Yii::app()->getComponent($this->_connection->schemaCacheID))!==null)
    {
        foreach(array_keys($this->_tables) as $name)
        {
            if(!isset($this->_cacheExclude[$name]))
            {
                $key='yii:dbschema'.$this->_connection->connectionString.':'.$this->_connection->username.':'.$name;
                $cache->delete($key);
            }
        }
    }
    $this->_tables=array();
    $this->_tableNames=array();
    $this->_builder=null;
}

public function renameColumn($table, $name, $newName)
{
    return "ALTER TABLE ".$this->quoteTableName($table)
        . " RENAME COLUMN ".$this->quoteColumnName($name)
        . " TO ".$this->quoteColumnName($newName);
}

public function renameTable($table, $newName)
{
    return 'RENAME TABLE ' . $this->quoteTableName($table) . ' TO ' . $this->quoteTableName($newName);
}

public function resetSequence($table,$value=null)
{
}

public function truncateTable($table)
{
    return "TRUNCATE TABLE ".$this->quoteTableName($table);
}