Обсуждение: Re: Order by email address

Herve,

> toto@aol.com
> tutu@aol.com
> toto@be.com
> tutu@be.com
> toto@yahoo.com
> 
> Is it possible and how ?

Given the relational rule of Atomicity (each discrete piece of
information shall have its own column or row), the solution is for you
to make "e-mail id" and "domain" seperate fields. Then you can sort:
ORDER BY mailbox, domain

If this is a legacy database, and splitting the field is not an option
for you due to exisiting applications/policy, then you'll need to write
a custom sorting function:

CREATE FUNCTION email_sort (VARCHAR)
RETURNS CHAR(120) AS '
DECLAREemail_addr ALIAS for $1;mail_box CHAR(60);mail_domain CHAR(60);
BEGINmail_box := CAST(SUBSTR(email_addr, 1, (STRPOS(email_addr, ''@'', 1)
-1)) AS CHAR(60));mail_domain := CAST(SUBSTR(email_addr, (STRPOS(email_addr, ''@'', 1) +
1), 60) AS CHAR(60));RETURN mail_box || mail_domain;
END;'
LANGUAGE 'plpgsql';

Then:

SELECT user_id, email, email_sort(email) as sortcol
FROM users
ORDER BY sortcol;

However, this solution has a number of problems for data integrity down
the line. If e-mail addresses are that important to your application, I
greatly encourage you to split the field.

-Josh Berkus

P.S. Roberto, please add the above to our function library.
______AGLIO DATABASE SOLUTIONS___________________________                                      Josh Berkus Complete
informationtechnology      josh@agliodbs.com  and data management solutions       (415) 565-7293 for law firms, small
businesses       fax 621-2533   and non-profit organizations.      San Francisco
 

Herve, Etc.

Ooops!  A couple of misteaks in that last post:

> > toto@aol.com
> > tutu@aol.com
> > toto@be.com
> > tutu@be.com
> > toto@yahoo.com
> > 
> > Is it possible and how ?
> 
> Given the relational rule of Atomicity (each discrete piece of
> information shall have its own column or row), the solution is for
> you
> to make "e-mail id" and "domain" seperate fields. Then you can sort:
> 
>  ORDER BY mailbox, domain

I meant:ORDER BY domain, mailbox

> 
> If this is a legacy database, and splitting the field is not an
> option
> for you due to exisiting applications/policy, then you'll need to
> write
> a custom sorting function:
> 
> CREATE FUNCTION email_sort (VARCHAR)
> RETURNS CHAR(120) AS '
> DECLARE
>  email_addr ALIAS for $1;
>  mail_box CHAR(60);
>  mail_domain CHAR(60);
> BEGIN
>  mail_box := CAST(SUBSTR(email_addr, 1, (STRPOS(email_addr, ''@'', 1)
> -1)) AS CHAR(60));
>  mail_domain := CAST(SUBSTR(email_addr, (STRPOS(email_addr, ''@'', 1)
> +
> 1), 60) AS CHAR(60));
>  RETURN mail_box || mail_domain;

I meant:RETURN mail_domain || mail_box;

> END;'
> LANGUAGE 'plpgsql';
> 
> Then:
> 
> SELECT user_id, email, email_sort(email) as sortcol
> FROM users
> ORDER BY sortcol;
> 

-Josh

______AGLIO DATABASE SOLUTIONS___________________________                                      Josh Berkus Complete
informationtechnology      josh@agliodbs.com  and data management solutions       (415) 565-7293 for law firms, small
businesses       fax 621-2533   and non-profit organizations.      San Francisco