Date: 07/08/05 (MySQL Communtiy)    Keywords: php

hey guys, this is my first post in here - i'm also a member of php and flashdev

this seems simple, but i hope i don't bungle it up - i don't have a concrete example for this, just something i've been thinking about

let's say i have 2 tables, categories and items and there exists items.categoryID and category.ID;

is there an easy way to select only the categories that have associated items?


for instance:

if i have:
categories
----------
1. Category A
2. Category B
3. Category C
4. Category D
(1, 2, 3 and 4 being categories.id)

and

items
-----
1. Item A (items.categoryID = 1)
2. Item B (items.categoryID = 4)


can I, with just 1 select query, pull ONLY Category A (id = 1) and Category D (id = 4) to say, build a menu of categories, selecting only those categories that are "populated"?

in the past, how i've done this has been select ALL categories, then one at a time loop through the categories and do a SELECT statement for each ID and check for at least 1 result; then flag each category that has associated "stuff"; this is allright if the page you're building has to list all the products AND categories, but let's say I just want to build a menu of only available categories and not display any items (or not ALL the items) on a given page

any help is appreciated; let me know if that makes any sense...

Source: http://www.livejournal.com/community/mysql/61688.html