Message-ID: <44AEB4C6.9000903@numerixtechnology.de>
Date: Fri, 07 Jul 2006 20:23:50 +0100
From: T E Schmitz <mailreg@numerixtechnology.de>
Reply-To: mailreg@numerixtechnology.de
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To: pgsql-sql@postgresql.org
Subject: Re: SELECT substring with regex
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Rodrigo De Leon wrote:
> On 7/7/06, T E Schmitz <mailreg@numerixtechnology.de> wrote:
> 
>> But that takes me to the next problem:
>>
>> For the sake of the example I simplified the regular pattern.
>> In reality, BASE_NAME might be:
>>
>> 28mm
>> 28-70mm
>>
>> So the reg. expr. requires brackets:
>>
>> substring (NAME, '^(\\d+(-\\d+)?mm)' ) as BASE_NAME
>>
>> Actually, the pattern is more complex than that and I cannot see how I
>> can express it without brackets.
> 
> 
> Maybe:
> 
> select
> substring ('28-70mm LD AD Asp XR Macro', '^[\\d-]*mm' ) as BASE_NAME

Sorry, but that would also capture something like
10-30-59mm

The pattern describes either a single length (120 millimeters) or a 
range (30 to 70 millimetres), hence:

\\d+(-\\d+)?mm

The ? quantifier refers to the combination of '-' and digits and has to 
be bracketed.


If the brackets cannot be avoided in the expression, your original 
suggestion might come in handy though:

SELECT
substring (NAME, '^\\d+(-\\d+)?mm') AS BASE_NAME ,
substr(
     NAME
     , char_length(
         substring (NAME, '^\\d+(-\\d+)?mm')
     ) + 2
) AS SUFFIX


Still, I'd be interested to know whether there is a 'more elegant' solution.

-- 


Regards,

Tarlika Elisabeth Schmitz