Re: Query Challenge

Both the FROM and the WHERE clause follow the same rule of operating in reverse order where there is no other criterion for determining the order. But since joining takes precedence over filtering the effects of switching where clauses around are usually minimal.

--

Jonathan Lewis
Yet another Oracle-related web site: www.jlcomp.demon.co.uk

Jurij Modic wrote in message <36f2cd7e.5635501_at_news.siol.net>...
>On Fri, 19 Mar 1999 19:01:52 -0000, "Peter Jones"
><pete_at_pkjones0.demon.co.uk> wrote:
>
>>I've been taught that it's the order of the where clause that's important,
>>i.e. the comparisons should be in reverse order of preference.
>>
>>If this is not the case, please let me know so that I can change my
approach
>>;-(
>
>In my experiences Marc is absolutelly right. It's the order of the
>tables in the FROM clause that is important when RBO is used and
>nesteed loops are involved. The parser goes from the bottom up and
>from the right to left, so put the table that should be the driving
>table of the nesteed loop operation at the end of the list. The parser
>will get it first in the list and make it the driving table.
Received on Sat Mar 20 1999 - 01:43:52 CST