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Re: Select * in exists subq. (Was: Update table without where exists( subquery) ?

From: Roland Svensson <roland.svensson_at_localhost>
Date: Fri, 31 Mar 2000 10:57:34 +0200
Message-ID: <cro8eskjknuffshjffn9l4cmjcj9504qb1@4ax.com> 





On Thu, 30 Mar 2000 21:22:45 +0200, "Sybrand Bakker"
<postbus_at_sybrandb.demon.nl> wrote:


>


>First of all, replace the * in your subquery by a 'x'. You are now forcing


>Oracle to retrieve the row, using 'x' it won't retrieve the row.


>





Is this really true? Explain will not show any table access for an
exists subquery no matter what you put in the column-list (if there 
is a proper index). Optimizer seems to be smart enough to recognise
'exists' and skip all unnecessary row retrieval.




-- 


Regards,


Roland
Received on Fri Mar 31 2000 - 02:57:34 CST












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