From: Volkan YAZICI <yazicivo@ttmail.com>
To: Andreas <maps.on@gmx.net>
Cc: pgsql-sql@postgresql.org
Subject: Re: How to find double entries
References: <48056F5F.30507@gmx.net>
Date: Wed, 16 Apr 2008 09:15:42 +0300
In-Reply-To: <48056F5F.30507@gmx.net> (Andreas's message of "Wed, 16 Apr 2008
	05:15:43 +0200")
Message-ID: <87zlru72b5.fsf@alamut.mobiliz.com.tr>
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On Wed, 16 Apr 2008, Andreas <maps.on@gmx.net> writes:
> how can I find double entries in varchar columns where the content is
> not 100% identical because of a spelling error or the person
> considered it "looked nicer" that way?
>
> I'd like to identify and then merge records of e.g.   'google',
> gogle', 'guugle' 
>
> Then I want to match abbrevations like  'A-Company Ltd.', 'a company
> ltd.', 'A-Company Limited'
>
> Is there a way to do this?
> It would be OK just to list candidats up to be manually checked
> afterwards.

You can try something similar to below example. (levenshtein(text, text)
function is supplied by fuzzystrmatch module.)

SELECT T1.col, T2.col
  FROM tbl AS T1,
       INNER JOIN tbl AS T2
               ON T1.col <> T2.col AND
                  levenshtein(T1.col, T2.col) < (length(T1.col) * 0.5)


Regards.