I agree with Connor that it has zero effect on the optimizer, and that it
most likely was to make it easier to modify the view dynamically.
Either that or the author was some anal-nut-job that liked to see it for
some bizarre reason.
Tom Mercadante
Oracle Certified Professional
-----Original Message-----
Sent: Tuesday, October 21, 2003 8:05 AM
To: Multiple recipients of list ORACLE-L
I'm pretty sure the optimizer can pick up 1=1 anyway
and ignore it as an always-true condition - so you get
no benefit.
The most common cause I've seen for 1=1 is so when
developers are building dynamic where-clause, they
don't need to worry about adding 'where' versus 'and'
to the sql string being constructed.
hth
connor
- "Hately, Mike (LogicaCMG)"
<mike.hately_at_nedl.co.uk> wrote: > Morning folks,
>
> the developers here are looking at a view with a
> where clause which
> specifies :
>
> WHERE 1=1 AND
> ............... AND
> ............... etc.
>
> I'd seen this used before as a way of tweaking the
> RBO into certain
> behaviours but it was years ago and my recollection
> is very hazy.
> The only explanation I've found so far is :
>
> "the 1=1 is in there to avoid doing repetitive index
> scans for single
> rowids, when the app "knows" the result set is going
> to be manipulated
> rowid's for a large subset of the table. I would
> guess your DUAL/CBO example
> had some similar effect."
>
> Is anyone familiar enough with this tweak to explain
> it ?
>
> Cheers,
> Mike
>
> PS Maybe it'll head off some replies if I make it
> clear that this view
> hasn't been generated by code so the "1=1" isn't an
> accidental artifact It
> was custom written and is definitely supposed to
> have exactly this
> structure.
>
>
>
>
>
>
>
>
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Received on Tue Oct 21 2003 - 08:09:26 CDT
