From: greg@turnstep.com
To: pgsql-sql@postgresql.org
Cc: sgnerd@yahoo.com.sg
Cc: sgnerd@yahoo.com.sg
Subject: Re: Equivalent of Reverse() functions
In-Reply-To: <00cb01c3b4b2$c23d9520$7502a8c0@hdsc.com>
Date: Sat, 29 Nov 2003 17:51:10 -0000
Message-ID: <c868f12fac1afa8fcf1a4e25eb33e81d@biglumber.com>


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> I am migrating an SQL Server 2000 database to Postgres 7.3.4 running
> on RH Linux 7.2. While migrating I encounter SQL Server REVERSE( )
> function, seems no such functions at Postgres.
>
> Is there a equivalent function available at Postgres? Please
> shed some light
 
No. If you have plperl installed, as somebody already posted, you can
take advantage of perl's built in reverse() function. Here is a
plpgsql version:
  
CREATE OR REPLACE FUNCTION reverse(TEXT) RETURNS TEXT AS '
  DECLARE
    original ALIAS FOR $1;
    reversed TEXT := \'\';
    onechar  VARCHAR;
    mypos    INTEGER;
  BEGIN
    SELECT LENGTH(original) INTO mypos;
    LOOP
      EXIT WHEN mypos < 1;
      SELECT substring(original FROM mypos FOR 1) INTO onechar;
      reversed := reversed || onechar;
      mypos := mypos -1;
    END LOOP;
    RETURN reversed;
  END
' LANGUAGE plpgsql IMMUTABLE RETURNS NULL ON NULL INPUT;
  
pg=> SELECT reverse('A man, a plan, a canal, Panama');
 
            reverse
- --------------------------------
 amanap ,lanac a ,nalp a ,nam A
 
 
- --
Greg Sabino Mullane greg@turnstep.com
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