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Date: Fri, 17 Feb 2012 15:52:13 +0800
From: John Tuliao <jptuliao@eglobalreach.net>
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To: "pgsql-sql@postgresql.org" <pgsql-sql@postgresql.org>
Subject: How can I use this subselect properly in an update?
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select
     substring(t1.called_number from t2.offset),
     t1.called_number
from
     calls_join as t1,
     john_prefix as t2
where
     strpos(t1.called_number, t2.prefix) = '1'
     order by length(t2.prefix) desc limit '1' ;

I'm having trouble using this as a sub-select in an UPDATE. Most of the 
time it works. Then sometimes it doesn't.
Is there an issue with possible NULL values that can be found on table1 
(t1)?