Question

I have the following SQL statement:

    SELECT TOP 30
    a.ClassAdID,    -- 0
    a.AdTitle,      -- 1
    a.ClassAdCatID, -- 2
    b.ClassAdCat,   -- 3
    a.Img1,         -- 4
    e.Domain,       -- 5
    a.AdText,       -- 6
    a.RegionID,     -- 7
    a.IsEvent,      -- 8
    a.IsCoupon,     -- 9
    b.ParentID,     -- 10
    a.MemberID,     -- 11
    a.AdURL,        -- 12
    a.Location,     -- 13
    a.GroupID       -- 14
    FROM ClassAd a
    INNER JOIN ClassAdCat b ON b.ClassAdCatID = a.ClassAdCatID
    INNER JOIN Member d ON d.MemberID = a.MemberID
    INNER JOIN Region e ON e.RegionID = a.RegionID
    WHERE DATEDIFF(d, GETDATE(), a.ExpirationDate) >= 0
    AND PostType <> 'CPN'
    ORDER BY a.CreateDate DESC

I want to only show one from each GROUPID… How can I adjust the statement to achieve this as I am lost with DISTINCT, GROUP BY etc..

Any help would be appreciated.

Many thanks,

Paul

Answer 1

You can use ROW_NUMBER function to partition data set based on GroupId values thus: for every new GroupId values the counter is restarted from 1 and the first row (with ROW_NUMBER = 1) is the newest record (a.CreateDate DESC). Then, we filter all records having ROW_NUMBER = 1 .

SELECT TOP 30 *
FROM
(
    SELECT
    a.ClassAdID,    -- 0
    a.AdTitle,      -- 1
    a.ClassAdCatID, -- 2
    b.ClassAdCat,   -- 3
    a.Img1,         -- 4
    e.Domain,       -- 5
    a.AdText,       -- 6
    a.RegionID,     -- 7
    a.IsEvent,      -- 8
    a.IsCoupon,     -- 9
    b.ParentID,     -- 10
    a.MemberID,     -- 11
    a.AdURL,        -- 12
    a.Location,     -- 13
    a.GroupID,      -- 14
    ROW_NUMBER() OVER(PARTITION BY a.GroupId ORDER BY a.CreateDate DESC) AS PseudoId
    FROM ClassAd a
    INNER JOIN ClassAdCat b ON b.ClassAdCatID = a.ClassAdCatID
    INNER JOIN Member d ON d.MemberID = a.MemberID
    INNER JOIN Region e ON e.RegionID = a.RegionID
    WHERE DATEDIFF(d, GETDATE(), a.ExpirationDate) >= 0
    AND PostType <> 'CPN'
) q
WHERE q.PseudoId = 1;