Re: Working with tables, best method

I've been told that if you have selection of the second table and you put
it in the join instead of the where... you'll be filtering records from the
second table before the join actually occurs. Of course you still need to
have the selection of fields in a proper order where a good index would be
used.


Michael Schutte
Admin Professional
Bob Evans Farms, Inc.

rpg400-l-bounces@xxxxxxxxxxxx wrote on 02/15/2008 08:44:40 AM:

Michael_Schutte@xxxxxxxxxxxx wrote:

I've never seen this brought up before so I thought I'll put this out
there. I can explain why but maybe someone else could. I've found

that if

you join tables together that it's better that you put your where

clause in

the join instead of the "where". Also putting the smaller table

first

seems to help.

It's interesting, but from what I remember from people who probably have
forgotten more about SQL than I know (people like Birgitta), the
position of the where doesn't really matter on a JOIN, it all gets
parsed down to the same code. However, the ordering of the tables can
have significant impact, especially if you have additional filtering
criteria. Which makes sense; if you have a file with order numbers to
process, you don't read every record in the order file and chain to the
list of orders to see if you should process it; you read the orders to
process and chain to the order file.

Joe
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