Oracle FAQ | Your Portal to the Oracle Knowledge Grid |
Home -> Community -> Usenet -> c.d.o.server -> Re: fix to heavy disk-read query?
hi,
Jonathan Lewis wrote in message
<933059182.26064.0.nnrp-01.9e984b29_at_news.demon.co.uk>...
>David Sisk wrote in message ...
>>You've got the right idea, though. Adding indexes is one of the best ways
>>to reduce the run-time of queries that do lot's of disk reads.
>
>I would rate it as the second best way.
>The best is to determine what the query is
>trying to do and figure out optimum
>strategy before doing anything else.
>
Very true. You might get answers on a question you didn't ask.
>In the case the query seems to be
>select order/balance for all orders
>where one of the order items is
>for a specific account.
>
>First action, therefore, is to determine
>whether you want the select on order_item
>to drive the query.
>
>Before worrying too much about that
>though, I would question why the BALANCE
>table with alias IB has no apparent join
>condition to the rest of the tables - did you drop
>a line as you copied the code, or is it really
>missing.
>
Make sure your joins implement the relationships between the tables as designed(?!!). You could end up with a cartesion join. I also don't see any point in using the part 'AND EXISTS .... ' in this case.
>
>--
>
>Jonathan Lewis
>Yet another Oracle-related web site: www.jlcomp.demon.co.uk
>
>
>
>
Received on Wed Jul 28 1999 - 07:32:51 CDT