Message-ID: <20040501142916.42206.qmail@web20803.mail.yahoo.com>
Date: Sat, 1 May 2004 07:29:16 -0700 (PDT)
From: Jeff Eckermann <jeff_eckermann@yahoo.com>
Subject: Re: isnumeric() function?
To: Yudie <yudie@axiontech.com>
Cc: pgsql-sql@postgresql.org
In-Reply-To: <001b01c42ec7$c64ed040$8401a8c0@home.axiontech.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii


--- Yudie <yudie@axiontech.com> wrote:
> Great the function works, but what does it means?
> SELECT $1 ~ ''^[0-9]+$''
> 
> Yudie

"~" is the regular expression match operator; the text
inside the quotes is a regular expression.  Look here
for a reference:

http://www.postgresql.org/docs/7.2/interactive/functions-matching.html#FUNCTIONS-REGEXP

The function definition in my note was intended as an
example; it won't necessarily do exactly what you
want.  For example, it will reject a decimal point (in
that case, try SELECT $1 ~ ''^[0-9]+(\\.[0-9]+)?$'').

If you are not familiar with regular expressions,
consider spending a little time learning about them. 
They are simply the best way to do pattern matching,
and if you do any amount of text processing at all,
time spent learning will repay you very well.

> 
> ----- Original Message ----- 
> From: "Jeff Eckermann" <jeff_eckermann@yahoo.com>
> To: "Yudie" <yudie@axiontech.com>;
> <pgsql-sql@postgresql.org>
> Sent: Friday, April 30, 2004 9:11 AM
> Subject: Re: [SQL] isnumeric() function?
> 
> 
> --- Yudie <yudie@axiontech.com> wrote:
> > What is isnumeric function in postgresql? 
> > I'm using psql version 7.2.2
> > thanks
> > Yudie
> 
> I don't think that function is included as such. 
> But
> you could do something like:
> 
> CREATE FUNCTION isnumeric(text) RETURNS boolean AS '
> SELECT $1 ~ ''^[0-9]+$''
> ' LANGUAGE 'sql';
> 
> Note that you would need to create this function for
> every parameter datatype that you would intend to
> use,
> or else be prepared to cast your input datatype as
> appropriate.
> 
> > 
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