Tks!
This is a good solution... (and my first try)
But don't work, still read the whole table for the yearorden given.

I found a couple of "unoptimized" black-point in my application.
And what it looks to be nice and wick became an pain in the ass.

--- In firebird-support@yahoogroups.com, fabianoaspro@... wrote:
>
> Create a descending index with yearorden and norden in this sequence. Thats
> it.
> Em 16/04/2013 04:57, "skander_sp" <skander_sp@...> escreveu:
>
> > **
> >
> >
> > Easy (and usual case)
> >
> > Simple table
> >
> > CREATE TABLE ORDENES (
> > ID_ORDEN INTEGER NOT NULL /* Primary key - GenId */
> > YEAR_ORDEN INTEGER NOT NULL /* Year of Orden */,
> > N_ORDEN INTEGER NOT NULL /* Order in the Year */,
> > ... /* no matter */
> > );
> >
> > ALTER TABLE ORDENES ADD CONSTRAINT UK_ORDENES UNIQUE (YEAR_ORDEN,
> > N_ORDEN)USING DESCENDING INDEX UK_ORDENES_YEAR_N_ORDEN;
> >
> > Now I need to access in the insert trigger, for next order to be assigned
> > to N_ORDEN in the YEAR_ORDEN using
> >
> > select coalesce(max(o.n_orden),0)+1
> > from ordenes o
> > where o.year_orden=new.year_orden
> > into new.n_orden
> >
> > IT WORK!!!! nice, BUT NOT OPTIMIZED, in the Performance Analisys it read
> > (indexed) all the N_ORDEN in the table, not going to the first (given the
> > descending order of the index)
> >
> > How can optimize the index/query?
> > Or simply is not possible doing more?
> >
> > Tks in advance
> >
> >
> >
>
>
> [Non-text portions of this message have been removed]
>