greatest-n-per-group

I have the following mySQL query that works perfectly fine. Except that I need to add a "FORCE INDEX" and I'm unsure on where I have to do this. I tried just about every location and always receive a mySQL error. What am I doing wrong? Here is the original query: $sql_select_recent_items = $db->query("SELECT * FROM (SELECT owner_id, product_id, start_time, price, currency, name, closed, active, approved, deleted, creation_in_progress FROM db_products ORDER BY start_time DESC) as resultstable WHERE resultstable.closed=0 AND resultstable.active=1 AND resultstable.approved=1 AND resultstable

Possible Duplicate: mysql: Using LIMIT within GROUP BY to get N results per group? I have a two tables: Items Categories Each item belongs to a category. What I want to do is select 5 items per category but say 20 items in total. SELECT item_id, item_name, items.catid FROM items, categories WHERE items.catid = categories.catid GROUP BY items.catid LIMIT 0,5 //5 per category group Edit: if there are more than 5 items per category - they should be ordered by the item_id (numeric value) Try this query - SELECT item_id, item_name, catid FROM (SELECT t1.*, COUNT(*) cnt FROM items t1 LEFT JOIN items