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Date: Fri, 17 Jun 2005 12:25:28 +0200
From: Andreas Kretschmer <akretschmer@despammed.com>
To: pgsql-sql@postgresql.org
Subject: Re: [despammed] substr or char_length problem
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am  17.06.2005, um 13:01:15 +0300 mailte Fatih Cerit folgendes:
> Dear ALL
> 
> I have a problem with function substr or char_length or both. I guery A2 
> and it works fine. But sometimes gives 'ERROR:  negative substring length 
> not allowed'. When I test many many times with diffrent values, never gives 
> error. Sample table and query below.
> 
> 
> 
> A1              A2
> -------------------
> 1               1957
> 2               197
> 3               19
> 4
> 5               NULL
> 6               1
> 7               195
> 
> 
> Select * from tbl_xxx where 
> tbl_xxx.A2=substr('196895588454554545454',0,char_length(tbl_xxx.A2)+1);

Perhaps because char_length() returns NULL and this is a invalid value
for substr(). Use coalesce():

... substr('196895588454554545454',0,coalesce(char_length(tbl_xxx.A2),0)+1);


Regards, Andreas
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