How do I JOIN another table to this code in SQL?

Question

I need to JOIN a table named IB to the code below. I need to pull in the following fields from IB: QOO, QOH, QCM and AVG. The JOIN conditions are IJ.IJITEM = IB.IBITEM and IJ.IJLOC = IB.IBLOC

;WITH cte AS 
    (
      SELECT IJLOC, IJITEM, IJDATE, IJLCGT,
        rn = ROW_NUMBER() OVER (PARTITION BY IJITEM, IJLOC ORDER BY IJDATE DESC)
      FROM dbo.IJ
    )
    SELECT IJLOC, IJITEM, IJDATE, IJLCGT
    FROM cte WHERE rn = 1;

Answer 1

One method, which allows for a little more complexity than just JOINing the IB table to "cte" in your final SELECT is to nest another CTE using the current one as the table. For example:

;WITH cte AS 
(
    SELECT IJLOC, IJITEM, IJDATE, IJLCGT,
    rn = ROW_NUMBER() OVER (PARTITION BY IJITEM, IJLOC ORDER BY IJDATE DESC)
    FROM dbo.IJ
),
filtered AS (
    SELECT IJLOC, IJITEM, IJDATE, IJLCGT
    FROM cte
    WHERE rn = 1
)
SELECT  ib.QOO, ib.QOH, ib.QCM, ib.[AVG]
FROM    ib
INNER JOIN filtered
        ON filtered.IJITEM = IB.IBITEM
        AND filtered.IJLOC = IB.IBLOC

Another option, depending on how the query optimizer handles the JOINs between all the tables, and if you don't need to return any of the fields from the IJ table, is to insert the results of your CTE into a temp table and then JOIN to that. For example:

CREATE TABLE #Temp (IJITEM DataType, IJLOC DataType)

;WITH cte AS 
(
    SELECT IJLOC, IJITEM, IJDATE, IJLCGT,
    rn = ROW_NUMBER() OVER (PARTITION BY IJITEM, IJLOC ORDER BY IJDATE DESC)
    FROM dbo.IJ
)
INSERT INTO #Temp (IJITEM, IJLOC)
    SELECT IJITEM, IJLOC
    FROM cte
    WHERE rn = 1;

SELECT  ib.QOO, ib.QOH, ib.QCM, ib.[AVG]
FROM    ib
INNER JOIN #Temp tmp
        ON tmp.IJITEM = IB.IBITEM
        AND tmp.IJLOC = IB.IBLOC

Answer 2

;
WITH    cte
          AS ( SELECT   IJLOC ,
                        IJITEM ,
                        IJDATE ,
                        IJLCGT ,
                        rn = ROW_NUMBER() OVER ( PARTITION BY IJITEM, IJLOC ORDER BY IJDATE DESC )
               FROM     dbo.IJ
             )
    SELECT  IJLOC ,
            IJITEM ,
            IJDATE ,
            IJLCGT ,
            IB.QOO ,
            IB.QOH ,
            IB.QCM ,
            IB.[AVG]
    FROM    cte
            INNER JOIN IB ON cte.IJITEM = IB.IBITEM
                             AND cte.IJLOC = IB.IBLOC
    WHERE   cte.rn = 1 ;