Thread: casting character varying to integer - order by numeric sort

How can I force a character field to sort as a numeric field?
I've got something like this:

Postgres=> SELECT username,last_name                 FROM eg_member ORDER BY username;
----------+-----------0120     | Foley1        | Sullivan10       | Guest11       | User
(5 rows)

(I can't change the field type).  I tried: SELECT username,last_name FROM eg_member ORDER BY username::integer;

But postgres 7 rejects this with "ERROR:  cannot cast type character 
varying to integer".  Is there a way to force numeric sort order?  I 
tried a variety of functions, such as to_char() and convert() without 
any luck.  Thanks for your insight!

Check out the function to_number()

In particular here's an example...
If a field named section is text containing numbers:
ORDER BY to_number(t.section, text(99999999))

If the field can also contain non-numerals such as 3a, 3b, and you want 
3a to show first then do this:
ORDER BY to_number(t.section, text(99999999)), t.section

And if the field section can actually START with an alpha, then to 
prevent to_number from failing do this:
to_number(textcat('0', t.section), text(99999999)), t.section

Terry

Bryce W Nesbitt wrote:
> How can I force a character field to sort as a numeric field?
> I've got something like this:
> 
> Postgres=> SELECT username,last_name
>                  FROM eg_member ORDER BY username;
> ----------+-----------
> 0120     | Foley
> 1        | Sullivan
> 10       | Guest
> 11       | User
> (5 rows)
> 
> (I can't change the field type).  I tried:
> 
>  SELECT username,last_name
>  FROM eg_member ORDER BY username::integer;
> 
> But postgres 7 rejects this with "ERROR:  cannot cast type character 
> varying to integer".  Is there a way to force numeric sort order?  I 
> tried a variety of functions, such as to_char() and convert() without 
> any luck.  Thanks for your insight!
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 2: Don't 'kill -9' the postmaster
> 

-- 
Terry Fielder
terry@greatgulfhomes.com
Associate Director Software Development and Deployment
Great Gulf Homes / Ashton Woods Homes
Fax: (416) 441-9085

Bryce W Nesbitt <bryce1@obviously.com> writes:
>   SELECT username,last_name
>   FROM eg_member ORDER BY username::integer;

> But postgres 7 rejects this with "ERROR:  cannot cast type character 
> varying to integer".

As a general rule, you need to be more specific than that about which
version you are working with ;-)

You may find that username::text::integer will work, depending on which
7.x this actually is.
        regards, tom lane

Tom Lane wrote:<br /><blockquote cite="mid3687.1129779194@sss.pgh.pa.us" type="cite"><blockquote type="cite"><pre
wrap="">Butpostgres 7 rejects this with "ERROR:  cannot cast type character 
 
varying to integer".   </pre></blockquote><pre wrap="">
As a general rule, you need to be more specific than that about which
version you are working with ;-)

You may find that username::text::integer will work, depending on which
7.x this actually is.
        regards, tom lane </pre></blockquote> Oooh, I'd be so happy to.  But I don't know.  Yes, I don't know.<br /><br
/>I know which version of "psql" is installed on my local machine, but the actual database is remote.  Is there a 
commandto get the server version?  As close as I can find is:<br /><br /> stage=> \copyright<br /> PostgreSQL Data
BaseManagement System<br /><br /> Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group<br /><br /><br
/>             -Bryce<br /><br /> PS: If it's a hint, "select username from eg_member order by username::text::integer"
worksfine.  Thanks.<br /> 

Bryce Nesbitt (mailing list account) wrote:
> Tom Lane wrote:

>>As a general rule, you need to be more specific than that about which
>>version you are working with ;-)

> Oooh, I'd be so happy to.  But I don't know.  Yes, I don't know.
> 
> I know which version of "psql" is installed on my local machine, but the actual 
> database is remote.  Is there a  command to get the server version?  As close as 
> I can find is:
> 
> stage=> \copyright

SELECT version();

--   Richard Huxton  Archonet Ltd

Cool, thanks.
PostgreSQL 7.4.2 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.2.3 
20030502 (Red Hat Linux 3.2.3-20)


Richard Huxton wrote:

> SELECT version();