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

If you really need total_comments in a separate table, I would make that a VIEW.

CREATE VIEW entry AS 
  SELECT id, COUNT(comments) AS total_comment 
  FROM comments 
  GROUP BY id

This way you avoid the maintenance task of updating the total_comments table altogether.