SQL LIMIT returns no results where no LIMIT returns results

You are repeating some of the conditions which is not necessary. Try this instead:

SELECT * FROM mm_tfs WHERE    (product_slug LIKE '%football%'  OR product_description LIKE '%football%')   AND schoolid = '8'    AND category_id ='21'LIMIT 4

UPDATE:

I have created the following table:

create table mm_tfs2 (schoolid varchar(2), categoryid varchar(2),                       description varchar(20), slug varchar(20));

And 5 times:

insert into mm_tfs2 values (8, 21, '', 'football');

And finally the query:

select * from mm_tfs2 where (slug like '%football%' and schoolid = 8 and categoryid = 21) or (description like '%football%' and schoolid = 8 and categoryid = 21) limit 4;+----------+------------+-------------+----------+| schoolid | categoryid | description | slug     |+----------+------------+-------------+----------+| 8        | 21         |             | football || 8        | 21         |             | football || 8        | 21         |             | football || 8        | 21         |             | football |+----------+------------+-------------+----------+4 rows in set (0.00 sec)

So I'm sorry to say that I'm not able to recreate the problem.

Try to put ( ) arround the entire condition

( (...AND...) OR (...AND...) )

Like so:

  SELECT * FROM mm_tfs WHERE   (  (product_slug LIKE '%football%' AND schoolid = '8' AND category_id ='21')    OR (product_description LIKE '%football%' AND schoolid = '8' AND category_id      ='21')  ) LIMIT 4

I think you could clean it up a little bit, you're getting only rows for one school, and one category ID, so there's no reason that you should have to check for those both times:

SELECT *FROM mm_tfsWHERE schoolid = '8'    AND category_id ='21'    AND (product_slug LIKE '%football%'         OR product_description LIKE '%football%')LIMIT 4;