How I can use 'OR' in my db queries

Question

What i really want is :

$query = db_select('watchdog', 'wa');
$query->orderBy('wa.timestamp', 'DESC')
        ->condition('blablabla', 'closed', '=') or 
          ('blablabla', 'blabla', '=')
           or ('blablabla', 'balblabla', '=')
        ->range(0, 20);
  $result = $query->execute();

I want to put many conditions with or but i do not know how to write them down..

Answer 1

The default is set to AND, to use or, you have to do like that

  $query = db_select('watchdog', 'wa');
    $query->orderBy('wa.timestamp', 'DESC');
    $or = db_or();
    $or->condition('blablabla', 'closed', '=');
    $or->condition('blablabla', 'blabla', '=');
    $or->condition('blablabla', 'balblabla', '=');
    $query->condition($or);
    $query->range(0, 20);

    $result = $query->execute();