SQL Server - Select first row that meets criteria

Question

I have 2 tables that contain IDs. There will be duplicate IDs in one of the tables and I only want to return one row for each matching ID in table B. For example:

Table

Answer 1

You should use PARTITION OVER to achieve the results.

   SELECT 
        t.objectIdA,
        t.objectIdB
    FROM (
      SELECT
         a.objectIdA,
         a.objectIdB,
        rowid = ROW_NUMBER() OVER (PARTITION BY a.objectIdA ORDER BY a.objectIdB DESC)
      FROM TableA a
       INNER JOIN TableB b ON (a.objectIdA = b.objectIdA)
    ) t
    WHERE rowid <= 1

Fiddle Code: http://sqlfiddle.com/#!3/a2ccd/1

Answer 2

SELECT  MAX(b.ID) AS ID
       ,MAX(Value) AS Value
       ,MAX(OtherCol1) AS OtherCol1
       ,MAX(OtherCol2) AS OtherCol2
       ,MAX(OtherCol3) AS OtherCol3
FROM TblA AS a 
INNER JOIN TblB AS b ON a.TblBID = b.ID
GROUP BY TblBID

Table A

Table B

Table A Data

Table B Data

Query Result

Answer 3

You can do so,by using a subselect for table a to get one entry per objectIdA group

select b.*,a.[objectIdB]
from b
join 
(select [objectIdA], max([objectIdB]) [objectIdB]
 from a group by [objectIdA]
) a 
on(b.[objectIdA] = a.[objectIdA])

Fiddle Demo

Edit deom comments to get a whole row from tablea you can use a self join for tablea

select b.*,a.*
from b
join a
  on(b.[objectIdA] = a.[objectIdA])
join (select [objectIdA], max([objectIdB]) [objectIdB]
 from a group by [objectIdA]) a1 
  on(a.[objectIdA] = a1.[objectIdA] 
     and 
    a.[objectIdB] = a1.[objectIdB])

Fiddle Demo 2

Answer 4

;WITH CTE
AS (
    SELECT  B.objectIdA
           ,A.objectIdB
           ,ROW_NUMBER() OVER (PARTITION BY B.objectIdA ORDER BY A.objectIdB DESC) rn
    FROM TableA A 
    INNER JOIN TableB B ON A.objectIdA = B.objectIdA
   )
SELECT C.objectIdA
      ,C.objectIdB
FROM CTE 
WHERE rn = 1