I know that mySQL 5.x does not support INTERSECT, but that seems to be what I need. Table A: Products (p_id) Table B: Prod_cats (cat_id) - category info (name, description, etc) Table C: prod_2cats (p_id, cat_id) - many to many prod_2cats holds the many (1 or more) categories that have been assigned to Products (A). Doing a query/filter lookup, (user interactive) and need to be able to select across multiple categories the products that meet ALL the criteria. Ex: - 80 products assigned to Category X - 50 products assigned to Category Y - but only 10 products (intersect) are assigned to BOTH cat X AND cat Y This sql works for one category: SELECT * FROM products WHERE p_show='Y' AND p_id IN ( SELECT p_id FROM prods_2cats AS PC WHERE PC.cat_id =" . $cat_id ." <-$cat_id is sanitized var passed from query form . I can't seem to find the means to say ' give me the intersect of cat A and cat B' and get back the subset (10 records, from my example) Help!