UFN_CONSTITUENT_GET_BY_CLIENTUSERID

create function dbo.UFN_CONSTITUENT_GET_BY_CLIENTUSERID
(
    @CLIENTUSERSID int
) 
returns uniqueidentifier 
as
begin
    declare @ID uniqueidentifier = null;

    select top 1 @ID = C.ID
    from dbo.CONSTITUENT C(nolock)
    inner join dbo.BackOfficeSystemPeople BOSP(nolock)
        on BOSP.BackofficeRecordID = C.SEQUENCEID and BOSP.BackOfficeSystemID = 0 
    inner join dbo.BackOfficeSystemUsers BOSU(nolock)
        on BOSU.BackofficePeopleID = BOSP.ID and BOSU.[CURRENT] = 1
    inner join dbo.ClientUsers CU(nolock)
        on CU.ID = bosu.ClientUsersID and CU.Deleted = 0 
        and CU.ID = @CLIENTUSERSID

    return @ID;
end