SQL When Case Function

create function CreateCode(@name nvarchar(50))
returns varchar (9) 
as
begin
declare @code varchar(9)

set @code = 
(
select
case
when @name like '%ERTÜRK%' then 'Kod1'
when @name like '%POLAT%' then 'Kod2'
else 'KodYok' end
  )
        
return @code 
end 


select dbo.CreateCode('ERTÜRK')
select dbo.CreateCode('POLAT')
select dbo.CreateCode('C#')