Re: Just as a learning exercise

From: Vit Spinka <vit.spinka_at_vitspinka.cz>
Date: Wed, 04 May 2011 21:40:36 +0200
Message-ID: <4DC1ABB4.3070702_at_vitspinka.cz>

Actually, 1=1 can do harm. If it is used in a join condition in outer join, the CBO cannot rewrite to (+) syntax and this limits its choice of join paths. This is not limited to "1=1", other conditions where the second table is not involved are affected as well (ie. when there is nothing where to put the "(+)").

I hit this on 10.2, and the disastrous results of 1=1 manifest even in 11.2.0.1.
(See http://vitspinka.blogspot.com/2009/07/latteral-view-quirk.html for an example.)

Vit

Dne 4.5.2011 16:46, Ric Van Dyke napsal(a):
> Roger that. That *IS* where it's useful as a place holder, but nothing
> more. The good old programming "sub", like writing a PL/SQL procedure
> with just
>
> BEGIN
> NULL;
> END;
>
> As the code, it's there and a call to the procedure will always work,
> because it does nothing! And it runs really fast too!
>
> But would adding a "NULL" to the top of every PL/SQL block make it run
> faster? I think we can all agree that it wouldn't, and logically that is
> about the same thing that adding 1=1 to your query.
>
> -----------------------
> Ric Van Dyke
> Hotsos Enterprises
> Cell 248-705-0624
> -----------------------
>
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> 4-8 March 2012 Start making plans now!
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>
>

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Received on Wed May 04 2011 - 14:40:36 CDT