Re: WHERE 1=2 with performance nightmares

Hi,

Usually the expression compiler will evaluate the expression to be false,
even before actually searching records.
Another way is where true=false (similar, but no potential ambiguity).


--
best regards
Kim Madsen
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www.components4developers.com

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"Craig Stuntz [TeamB]" <craig_stuntz@xxxxxxxxxxxxx [a.k.a. acm.org]> skrev i
en meddelelse news:46b1e43f$1@xxxxxxxxxxxxxxxxxxxxxxxxx
Kim Madsen wrote:

Sounds like a where clause added by an api or middleware to get the
field definitions but not any records.

It's not a good idea to do it that way, since any DB without an
expression index or an explicit "optimization" for nonsense will do a
full table scan on that. It's a far better idea to use a random PK
value, since that gets you 0 or 1 records, if you must do it this way
instead of using the system tables.

--
Craig Stuntz [TeamB] · Vertex Systems Corp. · Columbus, OH
Delphi/InterBase Weblog : http://blogs.teamb.com/craigstuntz
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