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UPDATE query help

Author

Topic

Apples
Posting Yak Master

146 Posts

Posted - 2008-10-17 : 17:43:29

Here's my schema and data:

------------------------------------------------
tblEntries
------------------------------------------------
EntryID | CommentCount
------------------------------------------------
1 | 0
2 | 0
------------------------------------------------

------------------------------------------------
tblComments
------------------------------------------------
CommentID | EntryID
------------------------------------------------
1 | 1
2 | 1
3 | 2
------------------------------------------------

I want to update the CommentCount for entries in tblEntries by passing in the CommentID's.

Here is my query:

UPDATE tblEntries
SET CommentCount = CommentCount + 1
WHERE EntryID IN (
SELECT EntryID
FROM tblComments
WHERE CommentID IN (1,2,3))

The subquery returns:
1
1
2

But when it goes to update the entries, Entry 1 only gets the CommentCount updated to 1 instead of 2. I assume it is because the 'WHERE EntryID IN (' clause doesn't deal with duplicates?

raky
Aged Yak Warrior

767 Posts

Posted - 2008-10-18 : 01:17:19

Try this

DECLARE @temp TABLE ( cnt INT, entryid int)
INSERT INTO @temp
SELECT COUNT(CommentID), entryid
FROM tblComments
GROUP BY entryid

UPDATE te
SET CommentCount = CommentCount + cnt
FROM tblEntries te
inner join @temp tc on ( tc.entryid = te.entryid)

SELECT * FROM tblEntries

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2008-10-18 : 01:54:36

or simply without using temp table

UPDATE t
SET t.CommentCount=t.CommentCount+c.cnt
FROM tblEntries t
INNER JOIN (SELECT COUNT(CommentID) AS cnt,EntryID
            FROM tblComments
            GROUP BY EntryID)c
ON c.EntryID=t.EntryID

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