如何使用单个MySQL查询更新表中的多个记录？

Question

I would like to update multiple records in a MySQL table using a single query. Basically, this is a tasks table, which has assignments for different people on different dates. When these assignments are changed and submitted via the Online form there is a lot of POST data that gets submitted (pretty much all the pending assignments). I've written an algorithm that sorts through all this information and gets what I want out of it, but I'm stuck on writing the query to update the MySQL table:

  // Find the modified records and save their information
  $update = 0;
  for ( $n = 0; $n < $total_records; $n++ )
  {
     if ( $_POST['update'.$n] == true )
     {
        $updates_arr[$update] = array( intval($_POST['user_id'.$n]), intval($_POST['task'.$n]), $_POST['date'.$n] );
        $update++;
     }
  }

  if ( $mysql_db = OpenDatabase() )
  {
     $query  = "UPDATE tasks_tbl";
     if ( $updates_arr[0] )
     {
        $query .= "   SET task = ".$updates_arr[0][1]." WHERE user_id = ".$updates_arr[0][0]." AND date = ".$updates_arr[0][2];
     }

     for ( $n = 1; $n < $updates; $n++ )
     {
        $query .= ",   SET task = ".$updates_arr[$n][1]." WHERE user_id = ".$updates_arr[$n][0]." AND date = ".$updates_arr[$n][2];
     }

     $result = mysql_query( $query, $mysql_db );

     if ( $result )
     {
        $page .= "<p>Success!</p>

";
     }
     else
     {
        $page .= "<p>Error: ".mysql_error()."</p>

";
     }
  }

This is the query that is generated:

UPDATE tasks_tbl 
   SET task = 1 
 WHERE user_id = 16 
   AND date = 2010-05-05,  
   SET task = 1 
 WHERE user_id = 17 
   AND date = 2222-02-22

Any suggestions would be appreciated. Thanks.

Answer 1

Thanks for the suggestions, everyone. I ended up going with the multiple queries, as it apparently was not going to be as simple to do, as I had hoped.

    foreach ( $updates_arr as $record => $data ):
       $query  = "UPDATE tasks_tbl";
       $query .= "   SET task = ".$data[1];
       $query .= "   WHERE task_id = ".$data[0];
       $result = mysql_query( $query, $mysql_db );
       if ( !$result )
       {
          break;
       }
       endforeach;