Problem with case when statement, when doing an insert.

Question

Hi there,  I have written the following coding, that has got an issue, due to not being allowed null values to be inserted into a column on a table.
,Case 
WHENCL.LocationISNOTNULLANDCL.[Floor]ISNOTNULLANDCL.RoomISNULLTHEN
(SELECTTop1
FL.FloorIDFROMPMIS.dbo.ConsentLocationF
JOINtbBuildingBONB.BuildingNumber=F.LocationCOLLATELatin1_General_CI_AS
JOINtbFloorFLONFL.BuildingID=B.BuildingID
WHEREF.Location=CL.LocationANDFL.FloorName=CL.[Floor]COLLATELatin1_General_CI_AS)
WHENCL.LocationISNOTNULLANDCL.[Floor]ISNOTNULLANDCL.RoomISNOTNULLTHEN
(SELECTTop1
R.RoomIDFROMPMIS.dbo.ConsentLocationF
JOINtbBuildingBONB.BuildingNumber=F.LocationCOLLATELatin1_General_CI_AS
JOINtbFloorFLONFL.BuildingID=B.BuildingID
JOINtbRoomRONR.FloorID=FL.FloorID
WHEREF.Location=CL.LocationANDFL.FloorName=CL.[Floor]COLLATELatin1_General_CI_ASANDR.RoomNumber=CL.RoomCOLLATELatin1_General_CI_AS)
ENDasParentID
I have written this case when statement above to find a ParentID.  I have got the case when statement to work individually, e.g. I get the correct records back.  However when I put it into a insert statement, as I want this ParentID to go
into a column in a table I get an error with the following message. 
Cannot insert the value NULL into column 'ParentID', table 'K2_Master_4_Test.dbo.tbConsentLink'; column does not allow nulls. INSERT fails.
Can someone point me in the right direction, as to what I need to do to get this case when statement working?  Also no I cannot change the structure of the table to allow for null values either.  So I need to modifiy this one.

Answer 1

The error is valid because your table column has 'not null' constraint and when your case expression does not satisfy  either of the 'when' conditions, it is returning NULL to the insert statement.
you can get around this by defining a generic value. Simple Example
select case when <<Column>>=1 then 'First' When <<Column>>=2 then 'Second' Else 'Last' End
In this case, when column value is not 1 or 2, it will insert 'Last'.
So, you have to do something like this...i.e add ELSE condition to your case..
Hope it Helps!!