Question

I have the following tables:

CATEGORIES —
entry_id, cat_id

TITLES — entry_id, title

DATA — entry_id, date, body

For each record entered into the DB the same entry_id is entered into all three entry_id fields in the three tables. In the Categories table, it will post a record for each category I’ve such as:

entry_id: 100 cat_id:24

entry_id: 100 cat_id:31

entry_id: 100 cat_id:17

(say cat_id 24 is web_design, 31 is coding and 17 is ajax)

THE PROBLEM: I’m having a bugger of a time selecting only records that have a record for BOTH cat_id 24 and 17 in the Categories table along with other fields. Here’s what I’ve got. I know it’s crude but it gets me almost all the way there:

SELECT 
    data.entry_id,
    data.date,
    data.body,  
    titles.entry_id,
    titles.title AS biz_name,
    categories.entry_id,
    categories.cat_id
    FROM data, titles, categories
    WHERE data.entry_id = titles.entry_id 
    AND data.entry_id = categories.entry_id 
    AND categories.cat_id = '24'

This will display everything with a cat_id of 24 but when I add

AND categories.cat_id = '17'

to the very end of the query, nothing is returned.

Any thoughts?

Answer 1

SELECT 
data.entry_id,
data.date,
data.body,  
titles.entry_id,
titles.title AS biz_name,
FROM data
JOIN titles ON data.entry_id = titles.entry_id
INNER JOIN categories cat1 ON data.entry_id = cat1.entry_id AND cat1.cat_id=17
INNER JOIN categories cat2 ON data.entry_id = cat2.entry_id AND cat2.cat_id=24
WHERE ((cat1.cat_id) = (17)) AND ((cat2.cat_id) = (24))

This new query correctly filters for only the ones with both