UFN_EVENTLODGINGROOMINSTANCE_ROOMNUMBER_UNIQUE

create function dbo.UFN_EVENTLODGINGROOMINSTANCE_ROOMNUMBER_UNIQUE
(
    @ROOMNUMBER nvarchar(10),
    @EVENTLODGINGID uniqueidentifier
)
returns bit
with execute as caller
as begin
    if @ROOMNUMBER = N''
        return 1;
    else
    begin
        declare @ROOMCOUNT int = 0;
        select
            @ROOMCOUNT = count(ID)
        from
            dbo.EVENTLODGINGROOMINSTANCE
        where
            ROOMNUMBER = @ROOMNUMBER
            and EVENTLODGINGID = @EVENTLODGINGID;

        if @ROOMCOUNT <= 1
            return 1;
    end

    return 0;

end