You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ') ORDER BY RAND( ) LIMIT 0 , 50' at line 4

SELECT `video_id`
FROM `video_categories`
WHERE `category_id`
IN ( SELECT `category_id` FROM `video_categories` WHERE `video_id` = )
ORDER BY RAND( )
LIMIT 0 , 50