Re: More efficient OR

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От KÖPFERL Robert
Тема Re: More efficient OR
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Msg-id ED4E30DD9C43D5118DFB00508BBBA76EB165CF@neptun.sonorys.at
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Ответ на More efficient OR  ("Keith Worthington" <keithw@narrowpathinc.com>)
Список pgsql-sql
At least for between, I read that pgSQL rewrites it to a  (a<x) AND (x<b).
And my experience shows that IN is translated into a series of ORs. 
I may be wrong

> -----Original Message-----
> From: Keith Worthington [mailto:keithw@narrowpathinc.com]
> Sent: Mittwoch, 16. Februar 2005 17:36
> To: PostgreSQL SQL
> Cc: Sean Davis; Scott Marlowe
> Subject: Re: [SQL] More efficient OR
> 
> 
> > > Hi All,
> > >
> > > In several of my SQL statements I have to use a WHERE clause
> > > that contains mutiple ORs.  i.e.
> > >
> > > WHERE column1 = 'A' OR
> > >       column1 = 'B' OR
> > >       column1 = 'C'
> > >
> > > Is there a more efficient SQL statement that accomplishes the
> > > same limiting functionality?
> > >
> > > Kind Regards,
> > > Keith
> > >
> >
> > Scott wrote:
> > The in() construct is (nowadays) basically the same as
> > ORing multiple columns;
> > 
> > where column1 in ('A','B','C') 
> > 
> > 
> > Sean Davis wrote
> > Could 'in' or 'between' do what you want?  I know that using 'in'
> > is equivalent to what you have below.  Could 'between' be more 
> > efficient--you could do explain analyze on various options to see 
> > what the actual plan would be.
> > 
> > Sean
> 
> Thanks Scott and Sean for the post.
> 
> It sounds like IN will save some typing and code space but 
> not decrease the
> execution time.
> 
> BETWEEN won't work for my real life query because the 
> limiting values are
> quite disparate.
> 
> Kind Regards,
> Keith
> 
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