How do I perform a GROUP BY on an aliased column in MS-SQL Server?

Question

I\'m trying to perform a group by action on an aliased column (example below) but can\'t determine the proper syntax.

SELECT       LastName + \', \'         


        

Answer 1

SELECT 
CASE WHEN LastName IS NULL THEN FirstName         
     WHEN LastName IS NOT NULL THEN LastName + ', ' + FirstName     
END AS 'FullName' 
FROM  customers GROUP BY 1`