UFN_CONSTITUENT_ISSTAFF

            CREATE function dbo.UFN_CONSTITUENT_ISSTAFF(@CONSTITUENTID uniqueidentifier) 
            returns bit
            with execute as caller
            as begin
                declare @CURRENTDATE date;
                set @CURRENTDATE = getdate();

                if exists(
                    select
                        ID
                    from
                        dbo.STAFFDATERANGE
                    where
                        STAFFDATERANGE.CONSTITUENTID = @CONSTITUENTID and
                        (STAFFDATERANGE.DATEFROM <= @CURRENTDATE or STAFFDATERANGE.DATEFROM is null) and
                        (STAFFDATERANGE.DATETO >= @CURRENTDATE or STAFFDATERANGE.DATETO is null)
                ) return 1;

                return 0;
            end