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Re: Question about pattern matching

From: Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>
To: dimitris(dot)sakellarios(at)telesuite(dot)gr
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Question about pattern matching
Date: 2008-12-23 17:16:02
Message-ID: 49511CD2.20208@postnewspapers.com.au (view raw or flat)
Thread:
Lists: pgsql-general
dimitris(dot)sakellarios(at)telesuite(dot)gr wrote:
> TABLENAME
> 
> id    Candidate pattern
> -------------------------
> 1    0089258068520
> 2    008925806852
> 3    00892580685
> 4    0089258068
> 5    008925806
> 6    00892580
> 7    0089258
> 8    008925
> 9    00892
> 10    0089
> 11    008
> 12    00
> 13    0
> 
> 
> PATTERN
> -------
> 0089257000000
> 
> QUESTION
> --------
> Pls let me know which is the best way to match the
> following pattern against this table and Receive id = 8
> that is the longest matching pattern from left to right.

The simplest way would be to select the id of the record with
max(length(pattern)), using a WHERE clause to filter for only matching
patterns by comparing the substring of both pattern and teststr of
length min(length(pattern),length(teststr)) for equality.

--
Craig Ringer

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