Re: Query Optimization question

In article <39A27459.703_at_yahoo.com>,
  connor_mcdonald_at_yahoo.com wrote:
> vk02720_at_my-deja.com wrote:
> >
> > What is a good way to analyze slow running queries ?
> > Does the order of table names after 'from' or clauses after 'where'
> > matter ? If so are there anu rules of thumb to for from and where ?
> >
> > DBMS : Oracel 7.3.4 / 8.1.6
> > OS: AIX 4.2.x 4.3.x
> >
> > Any answers or pointers to info on the web appreciated.
> >
> > TIA
> >
> > Sent via Deja.com http://www.deja.com/
> > Before you buy.
>
> The answer as always is... depends
>
> If you are using rule based optimiser, the query is evaluated based on
> its syntax - thus table order etc is important. If you are using cost
> based optimiser, then Oracle tries to make an informed decision about
> the best way of going about things...
>
> The ANALYZE command is used to keep these stats up to date.
>
> HTH
> --
> ===========================================
> Connor McDonald
> http://www.oracledba.co.uk
>
> We are born naked, wet and hungry...then things get worse
>

I am not explicitly using any particluar optimizer. What is the difference in rule based or cost based optimizer ? Does Oracle select an optimizer by default. If so how do I specify one ? I read about the autotrace option and EXPLAIN PLAN a little bit. On my site the PLAN_TABLE does not exist and I do not control its creation. Is it always a good idea for it to exist ? Does this affect the performance of queries ?
Any general rules for the order of table names and where clauses in a query ?

Sent via Deja.com http://www.deja.com/
Before you buy. Received on Tue Aug 22 2000 - 16:41:08 CDT