Re: UPDATE problem

Ralf-Henning Glomb <glomb_at_ralf-henning-glomb.de> wrote in message news:<3BEAF91E.DB0F7175_at_ralf-henning-glomb.de>...
> Hi,
>
> i'm looking for a hint, how to write a update-statement for the
> following problem.
>
> I have table A filled with data.
> Now i want to update one attrbute (attrib_dest). The source is
> attrib_source from another table (tab2). The association between the two
>
> tables is tab1.key and tab2.key (both primary keys).
>
> The problem is, that i only want to update the rows on tab1 where the
> corresponding value of the source table is not NULL.
>
> So, teh following statement works, but it is much too slow.
>
> UPDATE tab1 a
> SET a.attrib_dest =
> ( SELECT b.attrib_source
> FROM tab2 b
> WHERE a.key = b.key
> )
> WHERE tab1.key IN
> ( SELECT c.key
> FROM tab1 c, tab2 d
> WHERE c.key = d.key
> AND d.attrib_source IS NOT NULL
> )
> ;
>
>
> It would be great if you could give me a hint how to write this
> statement in a better way.
>
> Thank you very much
>
> Ralf-Henning

UPDATE tab1 a
SET a.attrib_dest =

    ( SELECT b.attrib_source

        FROM  tab2 b
        WHERE a.key  = b.key
        and b.attrib_source is not null
     )

??

Zman Received on Fri Nov 09 2001 - 10:12:54 CST