MYSQL UPDATE with IN and Subquery

Question

Hi i have tables like this :

table entry :

id | total_comments
_____________________
1 | 0
2 | 0
3 | 0
4 | 0

Answer 1

Use:

UPDATE entry 
   SET total_comments = (SELECT COUNT(*)
                           FROM COMMENTS c
                          WHERE c.eid = id
                       GROUP BY c.eid)
 WHERE id IN ( SELECT eid 
                 FROM comments 
                WHERE id IN (1,2,3,4,5,6))