UFN_DESIGNATIONLEVELRECIPIENT_USERDEFINEDIDISUNIQUE

create function dbo.UFN_DESIGNATIONLEVELRECIPIENT_USERDEFINEDIDISUNIQUE
(
    @USERDEFINEDID nvarchar(100)
) 
returns bit
with execute as caller
as
begin
    declare @ISUNIQUE bit = 0;

    select 
        @ISUNIQUE = case when (count(*) <= 1) then 1 else 0 end
    from dbo.DESIGNATIONLEVELRECIPIENT
    where DESIGNATIONLEVELRECIPIENT.USERDEFINEDID = @USERDEFINEDID;

    return @ISUNIQUE;
end