Re: query performance -- revised!

I have no diea where this stuff with select 1 from dual comes from. I have never seen that.

however moving code to sub-queries and deciding to use an exists clause works well and is documented on asktom and in harrisons sql tuning book. It has worked for me before.

most of the improvements I have seen with the CBO is by considering the relative table sizes and how many rows you will return. There are several approaches that are better or worse depending on that.

Since his 'OR' is probably what is killing him. spinning it to a sub-query may help.

Sybrand Bakker <gooiditweg_at_sybrandb.demon.nl> wrote in message news:<j06bdvsprsun9o8c6o03907dti86p258el_at_4ax.com>...
> On Wed, 28 May 2003 17:28:18 -0700, "Mikito Harakiri"
> <mikharakiri_at_ywho.com> wrote:
>
> >Also consider the following:
> >5. Change the order of the tables in the from clause. Try all the
> >permutations.
> >6. Add "and exist(select 1 from dual)". Mix it with " and exist(select 2
> >from dual)" sparingly.
> >7. Try capital letters in the table names -- optimiser respect those more.
> >8. Start playing with init.ora parameters. There are too many of those to
> >check all the permutations, but give it a shot.
>
>
> He is running CBO, isn't he? So what will the suggestions above do?
> Apart from introducing stupid MYTHS, exactly NOTHING!!!!!
>
>
> Sybrand Bakker, Senior Oracle DBA
>
> To reply remove -verwijderdit from my e-mail address
Received on Thu May 29 2003 - 06:06:52 CDT