SQL's stored procedure - sql

Question

Select #vCtlPeriod = period from ctl
IF #vCtlPeriod = #Period
Begin
SET #vHdr = 'StkHdr'
SET #vDtl = 'StkDtl'
End
ELSE
Begin
SET #vHdr = 'HStkHdr'
SET #vDtl = 'HStkDtl'
End
SELECT H.Loc, D.MatCod, D.MatQty, H.Slipno, H.SapWH,
P.InvPri, P.InvPri * D.MatQty as InvAmt, P.ProCat, P.MaiGrp, P.SubGrp1,P.SerCod ,
SUBSTRING(Z.LotNum,1,4) As ProdMth, F.UpdGSPI,
Class = Case WHen F.UpdGSPI = '9' Then 'D'
When Cast(SUBSTRING(Z.LotNum,1,2) AS INT) * 12 + Cast(SUBSTRING(Z.LotNum,3,2) AS INT)>= #vPerClsA Then 'A'
When Cast(SUBSTRING(Z.LotNum,1,2) AS INT) * 12 + Cast(SUBSTRING(Z.LotNum,3,2) AS INT)>= #vPerClsB Then 'B'
When Cast(SUBSTRING(Z.LotNum,1,2) AS INT) * 12 + Cast(SUBSTRING(Z.LotNum,3,2) AS INT)>= #vPerClsC1 Then 'C1'
When Cast(SUBSTRING(Z.LotNum,1,2) AS INT) * 12 + Cast(SUBSTRING(Z.LotNum,3,2) AS INT)>= #vPerClsC2 Then 'C2'
ELSE 'C3'
END,
FGType = Case F.UpdGSPI WHen '1' Then 'Production'
When '2' Then 'Trading'
When '3' Then 'Non GSPI'
When '9' Then 'DisContinue'
Else
'Not Maintain'
End,
FGSTATUS = Case When NOT ISNULL(Z.HolCod,'')='' or NOT ISNULL(Z.ResCod,'')='' Then 'Hold/Reserved'
When NOT ISNULL(Pd.Slipno,'')='' OR NOT ISNULL(Tg.Slipno,'')='' Then 'Pick'
ELSE ''
End,
Tg.SONum , Tg.Seq1, Tg.SptNum, Tg.Qty, Od.LPNum ,
Z.LotNum, Z.DocRefNo, IsNull(Z.HolCod,'') As HolCod, IsNull(Z.HolInf,'') As HolInf, IsNull(Z.ResCod,'') As ResCod, IsNull(Z.ResInf,'') As ResInf
FROM #vHdr H Join #vDtl D ON D.Slipno = H.Slipno And H.Period = #Period
Join Prd P ON D.MatCod = P.ProCod
Join LOCW L ON L.Loc = H.Loc AND L.Pickable <> 'Z' AND L.Putable <> 'Z' AND L.WhCod =H.SapWh
Join ZV00 Z ON Z.SlipNo = H.SlipNo
LEFT JOIN PrdFG F on F.Procod = D.MatCod
LEFT JOIN (SELECT Slipno, MatCod, Qty =Sum(QtyPck) from PickD group by Slipno, matcod) Pd on D.SlipNo = Pd.Slipno and D.MatCod = Pd.MatCod
LEFT JOIN TagLotQty Tg ON TG.SlipNo = D.SlipNo and Tg.procod = D.MatCod
LEFT JOIN OrdD Od ON Od.SONum = Tg.SONum and Od.Seq1 = Tg.Seq1
Above is some of my code in my stored procedure, I intend to check the current period from the ctl file, if the period is current period then I will get from current transaction table or else it will be retrieved from history transaction table.
But I failed at the last select statement. Can we predefined the table name in the variable?

Answer 1

No, we can't. You should use Dynamic SQL or move your SELECT into IF statement

Answer 2

Isn't it simpler to just:
Select #vCtlPeriod = period from ctl
IF #vCtlPeriod = #Period
Begin
SELECt A.*, B.* from StkHdr A Join StkDtl B ON A.Slipno = B.Slipno
End
ELSE
Begin
SELECt A.*, B.* from HStkHdr A Join HStkDtl B ON A.Slipno = B.Slipno
End

Answer 3

You have to use Dynamic SQL like this:
Select #vCtlPeriod = period from ctl
IF #vCtlPeriod = #Period
Begin
SET #vHdr = 'StkHdr'
SET #vDtl = 'StkDtl'
End
ELSE
Begin
SET #vHdr = 'HStkHdr'
SET #vDtl = 'HStkDtl'
End
declare #cmd varchar(500)
select #cmd = "SELECT A.*, B.* from " + #vHDr + " A Join " + #vHdtl + " B ON A.Slipno = B.Slipno "
exec (#cmd)