Do you know some SQL aggregate workrounds?

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I've got this table (without a primary key), I know this query isn't correct, but what's its correct equivalent ?

SQL

SELECT siloid, amount, max(tdate)
FROM siolstate
GROUP BY siloid

I want to get all the rows in "siolstate" table which has the latest dates for each silo, I mean Grouped only by of field "siloid"

I thought about something like:

SQL

SELECT *
FROM siolstate
WHERE tdate = (SELECT siloid, max(tdate) FROM siolstate GROUP BY siloid)

but it won't work cause the subquery has two fields

and I thought about this too:

SQL

SELECT *
FROM siolstate
WHERE max(tdate)

but you know ... you can't use aggregation inside WHERE clause.

so ... any ideas?

Posted 10-Jun-10 12:28pm

Speed.Of.Light

Updated 10-Jun-10 12:39pm

v2

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2 solutions

Solution 2

How about this approach

SQL

SELECT *
FROM siolstate
WHERE tdate = (SELECT  max(tdate) FROM siolstate as a where siolstate.siloid = a.siloid)

Posted 11-Jun-10 22:30pm

Goutam Patra

Updated 11-Jun-10 22:38pm

v2

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**PSK_** · Accepted Answer · 2010-06-10T16:31:00

Solution 1

I think this is what your are looking for.

SELECT Temp.siloid, temp.tdate,MAIN.amount
FROM
( 
	select siloid, MAX(tdate) AS tdate
	from dbo.siolstate
	group by siloid
) Temp
INNER JOIN dbo.siolstate MAIN ON MAIN.siloid = Temp.siloid AND MAIN.tdate = Temp.tdate

Posted 10-Jun-10 16:31pm

PSK_

Comments

Speed.Of.Light 11-Jun-10 16:19pm

Thanks Prakash!
That's what I was looking for.