#1242 - Subquery returns more than 1 row - mysql

Question

I am trying to make a select statement that selects the image names from a MySQL database. The table is called - pictures_archive. I am also trying to select these pictures depending on the category they have. The code is:

SELECT pictures_archive_filename FROM pictures_archive 
WHERE pictures_archive_id = (SELECT pictures_archive_id 
FROM pictures_archive_category WHERE pictures_category_id = 9)

It gives me an "#1242 - Subquery returns more than 1 row" error. I can see why, but can't figure it out how to do it.

Answer 1

Since your subquery can return multiple values, IN should fit in youy where clause.

SELECT pictures_archive_filename 
FROM pictures_archive 
WHERE pictures_archive_id IN 
(
   SELECT pictures_archive_id 
   FROM pictures_archive_category 
   WHERE pictures_category_id = 9
)

an alternative for this is to join both tables which is more efficient.

SELECT  pictures_archive_filename 
FROM    pictures_archive a 
        INNER JOIN pictures_archive_category b
            ON a.pictures_archive_id = b.pictures_archive_id
WHERE   b.pictures_category_id = 9