CODEWITHSUNDEEP
mysqlsql-updatesubquerysql-view
Johal
Johal

Reputation: 607

MYSQL UPDATE with IN and Subquery

Hi i have tables like this :

table entry :

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

table comments :

id | eid | comment
_____________________
1 | 1 | comment sdfd
2 | 1 | testing testing
3 | 1 | comment text
4 | 2 | dummy comment
5 | 2 | sample comment
6 | 1 | fg fgh dfh

Query i write :

UPDATE entry 
   SET total_comments = total_comments + 1 
 WHERE id IN ( SELECT eid 
                 FROM comments 
                WHERE id IN (1,2,3,4,5,6))

Results i get is :

table entry :

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

Expected results :

table entry :

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

Any help will be appreciated.

Upvotes: 16

Views: 88981

Answers (5)

mluebke
mluebke

Reputation: 8809

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.

Upvotes: 3

Johal
Johal

Reputation: 607

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))

Upvotes: 0

OMG Ponies
OMG Ponies

Reputation: 332571

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))

Upvotes: 22

VeeArr
VeeArr

Reputation: 6178

Try:

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

Upvotes: 1

Satanicpuppy
Satanicpuppy

Reputation: 1587

That's exactly what I'd expect. The id is IN the set you give it, so total_comments = total_comments + 1.

It's not going to add one for each instance of the same value: that's not how IN works. IN will return a simple boolean yes/no.

Upvotes: 1

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