INSERT rows that do not exist

Question

I need to update (post) a table with summarized totals from another table. It is possible that the matching rows do not exist so I want to insert them before posting (UPDATE) to them. There is a table named BillingDetail that is summarized to insert into
another table named BillingHistory when rows do not match on 4 different columns. Below is my first shot at doing this but am not sure if the NOT IN clause is correct or maybe there is another (better) way.
INSERT INTO [dbo].[BillingHistory]
([entity]
,[plincd]
,[pgrpcd]
,[pitmcd]
,[hstyr]
,[corpnbr]
SELECT @entity
,plincd
,pgrpcd
,pitmcd
,@hstyr
,corpnbr
FROM (SELECT plincd
,pgrpcd
,pitmcd
,corpnbr
,SUM(qty) AS TotalQty
,SUM(extprc) AS TotalExtPrice
FROM dbo.BillingDetail
GROUP BY corpnbr, plincd, pgrpcd, pitmcd) AS DT
WHERE pitmcd NOT IN(SELECT pitmcd FROM dbo.BillingHistory WHERE plincd = DT.plincd AND pgrpcd = DT.pgrpcd AND pitmcd = DT.pitmcd AND corpnbr = DT.corpnbr);

Answer 1

Not knowing the keys of BillingHistory, it is difficult to say whether your INSERT is correct, but it does look funny. My guess is that all six columns constitute the key, in which case this would be better:
   INSERT INTO [dbo].[BillingHistory]
           ([entity]
           ,[plincd]
           ,[pgrpcd]
           ,[pitmcd]
           ,[hstyr]
           ,[corpnbr]
      SELECT @entity
           ,plincd
           ,pgrpcd
           ,pitmcd
           ,@hstyr
           ,corpnbr
      FROM (SELECT plincd
              ,pgrpcd
              ,pitmcd
              ,corpnbr
              ,SUM(qty) AS TotalQty
              ,SUM(extprc) AS TotalExtPrice
           FROM  dbo.BillingDetail
         GROUP BY corpnbr, plincd, pgrpcd, pitmcd) AS DT
              WHERE  NOT EXISTS (SELECT *
                                 FROM   dbo.BillingHistory BH
                                 WHERE  BH.entity = @entity
                                   AND  BH.plincd = DT.plincd
                                   AND  BH.pgrpcd = DT.prgpcd
                                   AND  BH.pitcmd = DT.pitcmd
                                   AND  BH.hstyr  = @hstyr
                                   AND  BH.corpnbr = DT.corpnbr)
And even better may be to use MERGE as Ronen suggested, but I want to see the CREATE TABLE statements (including keys) for the table before I try that.
Erland Sommarskog, SQL Server MVP, [email protected]