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help / color / mirror / Atom feedFrom: Guy Fraser <guy@incentre.net>
To: pgsql-sql@postgresql.org
Subject: Re: Regular Expressions
Date: Wed, 21 Mar 2007 14:32:26 -0600
Message-ID: <1174509146.26600.39.camel@sigurd.incentre.net> (raw)
In-Reply-To: <46016D43.9030300@fastcon.com.br>
References: <46013B89.4040603@fastcon.com.br>
<1174487806.26600.15.camel@sigurd.incentre.net>
<46016D43.9030300@fastcon.com.br>
On Wed, 2007-03-21 at 14:37 -0300, Ezequias R. da Rocha wrote:
> Guy Fraser escreveu:
> > On Wed, 2007-03-21 at 11:04 -0300, Ezequias R. da Rocha wrote:
> >
> >> Hi list,
> >>
> >> I would like to know if postgresql has a Regular Expressions (Regex)
> >> implemented already.
> >>
> >> With it we could implement queries like
> >>
> >> Select * from myClientes where name = 'E[zs]equias'
> >>
> >>
> > Case Sensitive Regular Match ~
> > Case Insensitive Regular Match ~*
> > Negated Case Sensitive Regular Match !~
> > Negated Case Insensitive Regular Match !~*
> >
> > Select * from myClientes where name ~ 'E[zs]equias'
> >
> >
> >> where the result occurs even if the field has Ezequias or Esequias.
> >>
> >> Regards
> >> Ezequias
> >>
> >> ---------------------------(end of broadcast)---------------------------
> >> TIP 2: Don't 'kill -9' the postmaster
> >>
> >>
> Great I am thinking of putting my like to rest. I felt it faster than
> "like" statement, have you any information about that ?
>
No I don't know if regular expressions are faster than "LIKE" but
I think they are more flexible. When developing queries, I usually
try different methods of matching to find out what works best for
each circumstance. Some times upper() lower() and substr() with an
"=" are more effective than other methods.
One of the more powerful features of PostgreSQL is the ability to
use sub-selects to reduce the time required to process a subset of
data from a larger volume of data.
Example :
select
*
from (
select
ss_time,
ss_date,
ss_type,
ss_data
from
full_set
where
ss_type in ('type_a','type_x')
) as sub_set
where
upper(ss_data) ~ '[A-Z][0-9][A-Z] ?[0-9][A-Z][0-9]'
order by
ss_time,
ss_date,
ss_type
;
> Ezequias
>
> ---------------------------(end of broadcast)---------------------------
> TIP 7: You can help support the PostgreSQL project by donating at
>
> http://www.postgresql.org/about/donate
>
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To: pgsql-sql@postgresql.org
Cc: guy@incentre.net
Subject: Re: Regular Expressions
In-Reply-To: <1174509146.26600.39.camel@sigurd.incentre.net>
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