Multiple CASE statements in SELECT

Hi Experts,

Can I use the result from one CASE statment in another? my SELECT statement is...

SELECT DISTINCT
                      dbo.tblMestecData.idMESTEC, dbo.tblMestecData.MESDATE, dbo.tblMestecData.LOCATION, dbo.tblMestecData.ALLOCATION, dbo.tblMestecData.OWNERSHIPTYPE,
                      dbo.tblMestecData.PARTNBR, dbo.tblMestecData.VERSION, dbo.tblMestecData.PARTDESCRIPTION, dbo.tblMestecData.QTY, dbo.tblMestecData.TRANSTYPE,
                      dbo.tblMestecData.REASONCODE, dbo.tblMestecData.REASONDESC, dbo.tblMestecData.TRANSCOMMENT, dbo.tblMestecData.GRNNBR,
                      dbo.tblMestecData.SERIALNBR, dbo.tblMestecData.CURRENCY, dbo.tblMestecData.UNITCOST, dbo.tblMestecData.TOTALBASELINECOST,
                      dbo.tblMestecData.COMPARTNBR, CASE WHEN OWNERSHIPTYPE = 'VMI Thales' AND UNITCOST > 0 THEN Price ELSE V1Price END AS DEFV1PRICE,
                      CASE WHEN OWNERSHIPTYPE = 'VMI Thales' AND UNITCOST > 0 THEN Currency ELSE NewCurrency END AS V1_CURRENCY,
                      CASE WHEN V1_CURRENCY = 'GBP' THEN 0 ELSE USD END AS EX_RATE

Im getting the error 'Invalid column name V1_CURRENCY'

Thanks,
Dean.
deanlee17Asked:
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CluskittConnect With a Mentor Commented:
That is because V1_CURRENCY is an alias. An alias is only applied to the final result. What you have to do is replace the V1_CURRENCY with the line that originated it:
CASE WHEN CASE WHEN OWNERSHIPTYPE = 'VMI Thales' AND UNITCOST > 0 THEN Currency ELSE NewCurrency END= 'GBP' THEN 0 ELSE USD END AS EX_RATE
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ingriTCommented:
You can't use VI_CURRENCY column that you have just created above, you should do something like this:

SELECT DISTINCT 
	dbo.tblMestecData.idMESTEC, dbo.tblMestecData.MESDATE, dbo.tblMestecData.LOCATION, dbo.tblMestecData.ALLOCATION, dbo.tblMestecData.OWNERSHIPTYPE, 
	dbo.tblMestecData.PARTNBR, dbo.tblMestecData.VERSION, dbo.tblMestecData.PARTDESCRIPTION, dbo.tblMestecData.QTY, dbo.tblMestecData.TRANSTYPE, 
	dbo.tblMestecData.REASONCODE, dbo.tblMestecData.REASONDESC, dbo.tblMestecData.TRANSCOMMENT, dbo.tblMestecData.GRNNBR, 
	dbo.tblMestecData.SERIALNBR, dbo.tblMestecData.CURRENCY, dbo.tblMestecData.UNITCOST, dbo.tblMestecData.TOTALBASELINECOST,
	dbo.tblMestecData.COMPARTNBR, CASE WHEN OWNERSHIPTYPE = 'VMI Thales' AND UNITCOST > 0 THEN Price ELSE V1Price END AS DEFV1PRICE, 
	CASE WHEN OWNERSHIPTYPE = 'VMI Thales' AND UNITCOST > 0 THEN Currency ELSE NewCurrency END AS V1_CURRENCY, 
		CASE WHEN OWNERSHIPTYPE = 'VMI Thales' AND UNITCOST > 0 AND Currency = 'GBP' THEN 0
		CASE WHEN NewCurrency = 'GBP' THEN 0
		ELSE USD END AS EX_RATE

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deanlee17Author Commented:
Ok so in a case statment how could I have multiple else statements....

CASE WHEN OWNERSHIPTYPE = 'VMI Thales' AND  UNITCOST > 0 THEN Currency ELSE V1Currency END
= 'GBP' THEN 0 ELSEIF
='EUR' then EURO ELSE
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The values for USD and EURO are stored in their own table.
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CluskittCommented:
You would have to use them on each statement:
CASE WHEN CASE WHEN OWNERSHIPTYPE = 'VMI Thales' AND UNITCOST > 0 THEN Currency ELSE NewCurrency END= 'GBP' THEN 0
WHEN CASE WHEN OWNERSHIPTYPE = 'VMI Thales' AND UNITCOST > 0 THEN Currency ELSE NewCurrency END='EUR' then EURO
ELSE 0 END
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ingriTCommented:
To have multiple case statements you can add case when ... then ... for every line until you set an else ..., that is the last statement in the case.
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CluskittCommented:
Another option would be to construct a smaller subquery as a table and use that as the field. Something like:
SELECT DISTINCT
                      dbo.tblMestecData.idMESTEC, dbo.tblMestecData.MESDATE, dbo.tblMestecData.LOCATION, dbo.tblMestecData.ALLOCATION, dbo.tblMestecData.OWNERSHIPTYPE,
                      dbo.tblMestecData.PARTNBR, dbo.tblMestecData.VERSION, dbo.tblMestecData.PARTDESCRIPTION, dbo.tblMestecData.QTY, dbo.tblMestecData.TRANSTYPE,
                      dbo.tblMestecData.REASONCODE, dbo.tblMestecData.REASONDESC, dbo.tblMestecData.TRANSCOMMENT, dbo.tblMestecData.GRNNBR,
                      dbo.tblMestecData.SERIALNBR, dbo.tblMestecData.CURRENCY, dbo.tblMestecData.UNITCOST, dbo.tblMestecData.TOTALBASELINECOST,
                      dbo.tblMestecData.COMPARTNBR, CASE WHEN OWNERSHIPTYPE = 'VMI Thales' AND UNITCOST > 0 THEN Price ELSE V1Price END AS DEFV1PRICE,
                      V1_CURRENCY,
                      CASE WHEN V1_CURRENCY = 'GBP' THEN 0 ELSE USD END AS EX_RATE
FROM MyTable INNER JOIN
(SELECT DISTINCT CASE WHEN OWNERSHIPTYPE = 'VMI Thales' AND UNITCOST > 0 THEN Currency ELSE NewCurrency END AS V!_CURRENCY, MyIDField ID2 FROM MyTable ON MyIDField=ID2

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You would have to adapt it to your complete query, but that is the theory. However, it would be more efficient to work with multiple cases, as those would require just a simple logical computation, instead of the creation and joining of a temporary table.
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deanlee17Author Commented:
Excellent info guys. I will award the points to Cluskitt's first answer.
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