Adding sub query - SQL Server 2008 - sql-server-2008

Question

I have following SQL query but this is not quite what I want:
SELECT
TOP (20) Attribs.ImageID AS ItemID
FROM
Attribs
LEFT OUTER JOIN
Items ON Attribs.ImageID = Items.ImageID
WHERE
(attribID IN ('a','b','c','d','e'))
AND (deleted NOT IN (1,2))
AND Attribs.attribID = 'a' AND Attribs.attribID = 'b'
GROUP BY
Attribs.ImageID
ORDER BY
COUNT(DISTINCT attribID) DESC
What I need is to query
AND Attribs.attribID = 'a' AND Attribs.attribID = 'b'
first, then rest of the WHERE clause based on the above query results.
Is this possible to achieve using sub query?
I'm using SQL Server 2008
Thank you

Answer 1

I'm not totally getting the reason why you want to do this one query first before the other.... but you could use a Common Table Expression (CTE) - something like this:
;WITH FirstQuery AS
(
SELECT a.ImageId
FROM dbo.Attribs a
WHERE a.attribID = 'a' AND a.attribID = 'b'
)
SELECT
TOP (20) a.ImageID AS ItemID
FROM
dbo.Attribs a
INNER JOIN
FirstQuery fq ON a.ImageId = fq.ImageId
LEFT OUTER JOIN
dbo.Items i ON a.ImageID = i.ImageID
WHERE
(attribID IN ('a','b','c','d','e'))
AND (deleted NOT IN (1,2))
GROUP BY
a.ImageID
ORDER BY
COUNT(DISTINCT attribID) DESC
With this, you first select the ImageID from your dbo.Attribs table in the CTE, and then join that result set with the result of the table and join to the Items table.

Answer 2

You want to do that for performance issues? Because splitting this up won't change the results.
Anyway, you can do this like:
SELECT TOP (20) rn_Attribs.ImageID AS ItemID
FROM (SELECT *
FROM Attribs
WHERE Attribs.attribID = '123' AND Attribs.attribID = '456') rn_Attribs
LEFT OUTER JOIN Items ON rn_Attribs.ImageID = Items.ImageID
WHERE(attribID IN ('a','b','c'))
AND (deleted NOT IN (1,2))
GROUP BY rn_Attribs.ImageID
ORDER BY COUNT(DISTINCT attribID) DESC