--- In firebird-support@yahoogroups.com, "Martijn Tonies" <m.tonies@u
...> wrote:

>
> > > > > Sorry for answering before properly reading the question...
> > > > >
> > > > > No, a DESCending index cannot be used with an ASCending

ORDER

> > BY.
> > > > You
> > > > > need two separate indexes if you want to index the field

both

> > > > > ASCending and DESCending.
> > > >
> > > > > Though note that too many indexes can be as
> > > > > bad as too few indexes, create only those that are likely to

be

> > > > > selective and useful.
> > > > >
> > > > > Set
> > > > >
> > > >
> > > > Indeed. This is the real problem. I display the data (let's

say

> > 50,
> > > > 000) rows in a grid with let's say 10 columns. Now the grid

can be

> > > > sorted by every column in ASC or DESC order. Imagine how this

will

> > > > look for 15 columns where I would have 30 indexes that slow

down

> > my
> > > > INSERTS, UPDATES and are very large because I have 50,000

rows.

> > > >
> > > > I don't get the reason for this unidirectional approach but to

me

> > is a
> > > > pain in the proverbial arse.
> > >
> > > Can't be as bad as showing 50000 rows in a grid :-)
> > >
> > > > Maybe there is another way of doing this, but the nature of

the

> > data
> > > > and of the software application forces me to do this.
> > >
> > >
> > > Sorting is independent of indices. If you want to retrieve all

the

> > rows,
> > > fetching them via an index is slower than fetching them straight
> > from
> > > disk and sorting them afterwards.
> >
> > My explanation was ambiguos. Let's try to clear the smoke:
> >
> > 1. I have a set of tables linked with several joins. The important
> > thing to know is that they are huge.
> > 2. The tables have a lot of columns, and most of them are shown in

the

> > grid to the user.
> > 3. I only display the rows that are visible (eg. fit in the

screen)

> > and of-course keep a local cache not to transfer them again.
>
> Are you showing (part of) a 50000 rows resultset or not? If so:

don't.

> Not even if you only "show" 50 visually. The server has to prepare

the

> resultset for you, this will take time.
>
> > Now: making two sets of indices for every shown column is going to
> > make my INSERTS/UPDATES slow and increase the size of the

database.

> >
> > Is there any other way to do this???
>
> With regards,
>
> Martijn Tonies
> Database Workbench - tool for InterBase, Firebird, MySQL, Oracle &

MS SQL

> Server
> Upscene Productions
> http://www.upscene.com

I didn't understand you last reply. My select is something like this
SELECT FIRST 50 SKIP 100 * FROM .....