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

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