SELECT * FROM table_name LIMIT 30

  SELECT * FROM table_name LIMIT 0 , 30

  SELECT * FROM table_name LIMIT $LimitOffset , $LimitRowCount

  SELECT group_id FROM group_channels WHERE group_id = $group_id LIMIT 1"

  SELECT group_id FROM group_channels WHERE group_id = $group_id ORDER BY device_id DESC LIMIT 1"