使用Yii Query Builder的SQL条件UNION（）

Question

i wanted to prepare one SQL query in which i wanted to put UNION query but that UNION query is based on certain condition, is it possible to make using Yii query builder.

below is sample code which i have made with simply DAO but i want to make it in query builder style

    if(isset($first) && $first!="")
       $con .= "SELECT id,first, from user where first LIKE '%".$first."%'";
   if(isset($last) && $last!="")
       $con .= " AND last LIKE '%".$last."%'";
   if((!empty($first) || !empty($last)) && (!empty($flag)) )
       $con .= " UNION SELECT id,first, from user where flag = 1"

   $command    = $connection->createCommand($con)->queryall();

Answer 1

Yes, it sure is. Assuming this were your test code:

$command = Yii::app()->db->createCommand();

if(<your if statements here) {
    $command->select('id, username, profile')
}

if(<union if statement>) {
    $command->union()
}

Some sample other lines from the Query Builder page

->from('tbl_user u')
->join('tbl_profile p', 'u.id=p.user_id')
->where('id=:id', array(':id'=>$id))
->queryRow();

But the main one you'll want to look at is union()