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

Try:

UPDATE entry
  SET total_comments = (SELECT COUNT(*) 
                        FROM comments
                        WHERE entry.id = comments.eid
                        GROUP BY id)