If else ladder using Case in sql server - sql

Question

I am trying to write if elif ladder in SQL but I am finding it little difficult to do that. My ladder looks like below.
IF (MortgageProduct.FreeLegalFees != NULL) THEN
IF(MortgageProduct.FreeLegalFees==1) THEN
Return TRUE as FreeLegalFees
ELSE
Return FALSE as FreeLegalFees
ELSE
IF (ConveyancerFee!=NULL) THEN
IF ConveyancerFee.AMOUNT = 0.0 then
Return TRUE as FreeLegalFees
ELSE
Return FALSE as FreeLegalFees
END IF
ELSE
IF (LenderFee!=NULL) THEN
IF LenderFee.AMOUNT = 0.0 then
Return TRUE as FreeLegalFees
ELSE
Return FALSE as FreeLegalFees
END IF
ELSE
Return TRUE as FreeLegalFees
END IF
I know that I have to use Case for that in SQL but I am confuse in writing Case statement in sql. Can somebody please help me to frame this ladder in sql server.

Answer 1

This is far more succinct. I have also aliased what I assume are your table names:
CASE WHEN MP.FreeLegalFees IS NOT NULL THEN IIF(MP.FreeLegalFees = 1,1,0)
WHEN CF.AMOUNT IS NOT NULL THEN IIF(CF.AMOUNT = 0,1,0)
WHEN LF.Amount IS NOT NULL THEN IIF(LF.AMOUNT = 0,1,0)
ELSE 1 END
/*
MP MortgageProduct
CF ConveyancerFee
LF LenderFee
*/

Answer 2

I would write this as:
(case when mp.FreeLegalFees = 1 then 1
when mp.FreeLegalFees is not null then 0
when cf.amount = 0.0 then 1
when cf.amount is not null then 0
when lf.amount = 0.0 then 1
when lf.amount is not null then 0
else 1
end) as FreeLegalFees

Answer 3

CASE
WHEN MP.FREELEGALFEES = 1 THEN 1
WHEN MP.CONVEYANCERLEGALFEESET IS NOT NULL THEN
(
CASE
WHEN (
(SELECT AMOUNT FROM CONVEYANCERLEGALFEE WHERE LOCATION=#p_iLocation
and TYPEOFAPPLICATION=#p_iTypeOfApplication
and TYPEOFBUYER=#p_iTypeOfBuyer and MAXIMUMVALUE=100000
and CONVEYANCERLEGALFEESETSTRTDATE <= (SELECT GETDATE())
and CONVEYANCERLEGALFEESET = MP.CONVEYANCERLEGALFEESET ) = 0.0)
THEN 1
ELSE 0
END
)
WHEN ((Select COUNT(FEESET) FROM LEGALFEE WHERE TYPEOFAPPLICATION=#p_iTypeOfApplication
AND FEETYPE = (Select VALUEID from COMBOVALUE where VALUENAME='Redeeming')) >= 1 ) THEN
(
CASE
WHEN (
(SELECT AMOUNT FROM LEGALFEE
WHERE TYPEOFAPPLICATION = #p_iTypeOfApplication
AND FEETYPE= (SELECT VALUEID FROM COMBOVALUE WHERE VALUENAME='Redeeming')) = 0.0)
THEN 1
ELSE 0
END
)
ELSE 1
This is the solution which works perfect. Thank you all.

Answer 4

CASE
WHEN MortgageProduct.FreeLegalFees IS NOT NULL
THEN (
CASE
WHEN MortgageProduct.FreeLegalFees = 1
THEN 'TRUE'
ELSE 'FALSE'
END
)
WHEN ConveyancerFee IS NOT NULL
THEN (
CASE
WHEN ConveyancerFee.AMOUNT = 0.0
THEN 'TRUE'
ELSE 'FALSE'
END
)
WHEN LenderFee IS NOT NULL
THEN (
CASE
WHEN LenderFee.AMOUNT = 0.0
THEN 'TRUE'
ELSE 'FALSE'
END
)
ELSE 'TRUE'
END AS FreeLegalFees