From: T E Schmitz <mailreg@numerixtechnology.de>
To: pgsql-sql@postgresql.org
Subject: Re: SELECT substring with regex
Date: Fri, 07 Jul 2006 20:23:50 +0100
Message-ID: <44AEB4C6.9000903@numerixtechnology.de> (raw)
In-Reply-To: <a55915760607071137q2c70346cp5b30cac14beaf1e7@mail.gmail.com>
References: <44AE66E0.1040606@numerixtechnology.de>
<200607071659.14940.gary.stainburn@ringways.co.uk>
<44AE9B4F.1020401@numerixtechnology.de>
<a55915760607071137q2c70346cp5b30cac14beaf1e7@mail.gmail.com>
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
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To: pgsql-sql@postgresql.org
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Subject: Re: SELECT substring with regex
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