Обсуждение: question on JOIN and WHERE clause

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question on JOIN and WHERE clause

От
Wei Weng
Дата:
Does the SQL optimizer process the JOIN first then add WHERE
constraintson it or it processes the WHERE clause and JOIN at the same
time?

Thanks!



-- 
Wei Weng
Network Software Engineer
KenCast Inc.




Re: question on JOIN and WHERE clause

От
"Henshall, Stuart - WCP"
Дата:
<p><font size="2">I believe it pushes any clauses it can into the individual sub-plans, and anything it can't it leaves
abovethe join.</font><br /><font size="2">- Stuart</font><p><font size="2">> -----Original Message-----</font><br
/><fontsize="2">> From: Wei Weng [<a href="mailto:wweng@kencast.com">mailto:wweng@kencast.com</a>]</font><br /><font
size="2">>Sent: 30 May 2002 18:07</font><br /><font size="2">> To: pgsql-sql@postgresql.org</font><br /><font
size="2">>Subject: question on JOIN and WHERE clause</font><br /><font size="2">> </font><br /><font
size="2">></font><br /><font size="2">> Does the SQL optimizer process the JOIN first then add WHERE</font><br
/><fontsize="2">> constraintson it or it processes the WHERE clause and JOIN at the same</font><br /><font
size="2">>time?</font><br /><font size="2">> </font><br /><font size="2">> Thanks!</font><br /><font
size="2">></font><br /><font size="2">> </font><br /><font size="2">> </font><br /><font size="2">> --
</font><br/><font size="2">> Wei Weng</font><br /><font size="2">> Network Software Engineer</font><br /><font
size="2">>KenCast Inc.</font><br /><font size="2">> </font><br /><font size="2">> </font><br /><font
size="2">></font>