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MySQL SELECT GROUP COUNT Query

Posted on 2011-09-26
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Last Modified: 2012-05-12
Hi,

I have a requirement to count 3 different amounts of content in a selected field.

My logic has written a query as follows, but this doesn't work as expected. Please can anyone shed some light?

Thanks,

Marty
SELECT
	A.FriendlyName,
	A.Delegates,
	COUNT(DISTINCT rU.ID_User) AS Registered,
	COUNT(DISTINCT aU.ID_User) AS Accepted,
	COUNT(DISTINCT pU.ID_User) AS Partial
	FROM
	ATL_V2_Affiliates AS A
	Left Join ATL_Users AS rU ON rU.ID_Affiliate AND rU.RegStatus='Registered'
	Left Join ATL_Users AS aU ON aU.ID_Affiliate AND aU.RegStatus='Accepted'
	Left Join ATL_Users AS pU ON pU.ID_Affiliate AND pU.RegStatus='Partial'
	GROUP BY
	A.ID_Affiliate
	ORDER BY
	A.FriendlyName;

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Question by:marty_t
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6 Comments
 
LVL 15

Expert Comment

by:Eyal
ID: 36598262
A.FriendlyName and A.Delegates should be also be included in the group by
and also do right joins
0
 
LVL 1

Author Comment

by:marty_t
ID: 36598283
I added the two fields in the Group By, but that makes no difference.

Using Right Joins instead of Left Joins gives zero rows.

I would like every row from "A" and counts from the others if they contain rows.

Thanks,

Marty
0
 
LVL 1

Author Comment

by:marty_t
ID: 36598306
This works as expected, but I would like to do it via joins instead.

Any ideas?

Thanks,

Marty
SELECT
	A.FriendlyName,
	A.Delegates,
	(SELECT COUNT(rU.ID_User) FROM ATL_Users AS rU WHERE rU.ID_Affiliate=A.ID_Affiliate AND rU.RegStatus='Registered') AS Registered,
	(SELECT COUNT(aU.ID_User) FROM ATL_Users AS aU WHERE aU.ID_Affiliate=A.ID_Affiliate AND aU.RegStatus='Accepted') AS Accepted,
	(SELECT COUNT(pU.ID_User) FROM ATL_Users AS pU WHERE pU.ID_Affiliate=A.ID_Affiliate AND pU.RegStatus='Partial') AS Partial
	FROM
	ATL_V2_Affiliates AS A
	ORDER BY
	A.FriendlyName;

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LVL 15

Expert Comment

by:Eyal
ID: 36598349
this query will have better performance. leave it like this
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LVL 15

Accepted Solution

by:
Eyal earned 1000 total points
ID: 36598356
Left Join ATL_Users AS rU ON rU.ID_Affiliate=A.ID_Affiliate AND rU.RegStatus='Registered'
Left Join ATL_Users AS aU ON aU.ID_Affiliate=A.ID_Affiliate AND aU.RegStatus='Accepted'
Left Join ATL_Users AS pU ON pU.ID_Affiliate=A.ID_Affiliate AND pU.RegStatus='Partial'
0
 
LVL 1

Author Closing Comment

by:marty_t
ID: 36598463
I cannot believe I let out the =A.ID_Affiliate

Such a schoolboy error, I've been writing these queries for over a decade and couldn't see the wood for the trees.

Many thanks for pointing out my error.

Marty
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