At 02:05 PM 27-06-00 +0000, you wrote:

>The reason why I asked about TOP N in the first place is that I use a
>3rd party DLL that uses TOP 1 to check if a database table is empty.
>
>This vendor prefers to do a TOP 1 rather than COUNT(*) because some
>databases do a full table scan to count the records. TOP 1
><i>hopefully</i> prevents this.
>
> -- John

Oh, that is so expensive! What about IF EXISTS() ?

Helen

>--- In IBDI@egroups.com, Ann Harrison <harrison@n...> wrote:
> >
> > >
> > >TOP isn't standard SQL and it's not a very sensible kind of thing
>to ask of
> > >a Client/Server database, given that the data isn't stored in any
>physical
> > >order. I'd be surprised if got anywhere near the top of anyone's
>list of
> > >"must-haves" for InterBase.
> >
> > There is one place where TOP<n> would be useful. Currently, an
>order
> > by clause causes InterBase to retrieve and sort the result set,
>unless
> > the order by terms match an index exactly and the query is simple
> > (single table?). In that restricted case, InterBase retrieves the
> > rows in index order. You probably think that index order would be
> > faster than sorting, but you would be wrong, in general. The one
>case
> > where walking in index order is reliably faster is when you want
>only
> > the TOP<n> rows. So TOP could be a nice hint to the optimizer.
> >
> > Ann
>
>
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