--- In firebird-support@yahoogroups.com, "Michael Vilhelmsen" wrote:

>
> Hi again
>
> Why is it, that you put a
>
> || ''
>
> after the
>
> Varer.Plu_Nr
>
> What effect does this have ?
>
> (Varer_Detail.VarePlu_ID = Varer.Plu_Nr || '' and

It prevents using an index for varer.plu_nr, whereas it is still
possible to use an index for varer_detail.vareplu_id. It is a way to
tell the optimizer to aviod certain indexes.

Set