Re: How is "UNION ALL " work in ORACLE ?

From: Jonathan Gennick <gennick_at_worldnet.att.net>
Date: 31 Jan 1999 01:12:04 GMT
Message-ID: <36c6a807.4878896@netnews.worldnet.att.net>

On Fri, 29 Jan 1999 08:56:24 GMT, yewpc_at_my-dejanews.com wrote:

>Hi,
>I don't understand how actually Oracle execute a SQL statement
>that has UNION ALL condition on it.

Look up the EXPLAIN PLAN statement in the SQL reference manual. You can use it to find out exactly how Oracle will execute any given query.

>Is there a way to force it to execute the 1st and 2nd select parallelly ?

My guess is that if you have parrellel server running, that Oracle would execute the two parts of a UNION ALL query in parellel. Again, I recommend using EXPLAIN PLAN to find out for sure.

Jonathan Received on Sat Jan 30 1999 - 19:12:04 CST