Du behöver kommatecken efter end
avslutar ärendet. Och "som" går efter case
uttalande, inte inuti det:
Insert into TblStuff(FullName, Address, City, Zip)
Select (Case When Middle is Null Then Fname + LName
Else Fname +' ' + Middle + ' '+ Lname
End) as FullName,
(Case When Address2 is Null Then Address1
else Address1 +', ' + Address2
End) as Address,
City as City,
Zip as Zip
from tblImport