UFN_REVENUE_GETORIGINALUNIQUERECEIPTNUMBER

create function dbo.UFN_REVENUE_GETORIGINALUNIQUERECEIPTNUMBER
            (
                @REVENUEID uniqueidentifier
            )
            returns nvarchar(20)
            with execute as caller
            as
            begin
                declare @RECEIPTNUMBER nvarchar(20);

                select top 1 
                    @RECEIPTNUMBER = coalesce(REC.UNIQUERECEIPTNUMBER, RR.UNIQUERECEIPTNUMBER)
                from 
                    dbo.REVENUERECEIPT RR 
                left join 
                    dbo.REVENUERECEIPT REC on RR.ORIGINALREVENUERECEIPTID = REC.ID
                where 
                    RR.REVENUEID = @REVENUEID
                order by 
                    RR.RECEIPTPROCESSDATE asc;

                return @RECEIPTNUMBER; 
            end