mySQL experts - need help with 'intersect'

Posted by MTCreations on Stack Overflow See other posts from Stack Overflow or by MTCreations
Published on 2010-04-05T20:46:28Z Indexed on 2010/04/05 21:03 UTC
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mysql

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intersect

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union

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select

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!

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