Subject Re: [firebird-support] Opimize query with casted field
Author Mitch Peek
Helen Borrie wrote:
> In Firebird 2.0.x you can have an expression index - see release notes.
> In Fb 1.5.x and below you'd need to add a trigger-populated proxy
> column for DyStart and index that, e.g.
> Alter DY add DyStartdate DATE;
> create index ascDyStartdate on DY (DyStartdate);
> create trigger biu_DY for DY
> active before insert or update
> as
> declare vtimestamp timestamp;
> begin
> if (new.DyStart is not null) then
> new.DyStartdate = cast (new.DyStart as Date);
> end
> else
> if (updating and old.DyStart is not null) then
> new.DyStartdate = null;
> end
Would this approach be better then an index on the timestamp and just
querying between Adate and Adate+1? if so, why?
The only problem I see might be the inclusion of the record which could
occur if an entry was exactly at midnight (00:00:00.0000)


No need for the variable.
and an extra "end" before the else