Solved! Was: Re: Select question

Madison Kelly wrote:
> Hi all,
>
>   I am pretty sure I've done this before, but I am drawing a blank on
> how I did it or even what commands I need. Missing the later makes it
> hard to search. :P
>
>   I've got Postfix working using PostgreSQL as the backend on a small,
> simple test database where I have a simple table called 'users' with a
> column called 'usr_email' which holds, surprisingly, the user's email
> address (ie: 'mkelly@test.com').
>
>   To tell Postfix where the user's email inbox is (to write incoming
> email to) I tell it to do this query:
>
> SELECT
>     substring(usr_email FROM '@(.*)')||'/'||substring(usr_email FROM
> '(.*)@')||'/inbox'
> AS
>     email_file
> FROM
>     users
> WHERE
>     usr_email='mkelly@test.com';
>
>   Which returns:
>
>        email_file
> -------------------------
>  feneon.com/mkelly/inbox
>
>   Now I want to move to a more complex database where the email name
> comes from 'users' -> 'usr_email' (ie: 'mkelly') and the domain suffix
> comes from 'domains' -> 'dom_name' (ie: 'test.com').
>
>   The problem is, I am limited to how I can tell Postfix to generate the
> query. Specifically, I can't (or don't know how to) tell Postfix to
> create a join or split the email address. I can only tell Postfix what
> table to query, what the SELECT field to use, and what column to do the
> WHERE on.
>
>   So, my question,
>
>   Can I create a 'virtual table' table (or some such) that would take
> something like?:
>
> SELECT email_file FROM virtual_table WHERE email_addy='mkelly@test.com';
>
>   Where the email_addy can be split to create this query:
>
> SELECT
>     b.dom_name||'/'||a.usr_email||'/inbox'
> AS
>     email_file
> FROM
>     users a, domains b
> WHERE
>     a.usr_dom_id=b.dom_id
> AND
>     a.usr_email='mkelly'
> AND
>     b.dom_name='test.com';
>
>   Which would still return:
>
>         email_file
> --------------------------
>  alteeve.com/mkelly/inbox
>
>   I hope I got the question across well enough. :)
>
>   Thanks all!
>
> Madi
>
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>

I got the answer from an Ian Peterson from the GTALUG. Thought I'd post
the answer here, "for the record".

-=-=-=-
CREATE VIEW
    email_file
AS SELECT
    u.usr_email || '@' || d.dom_name
AS
    email, d.dom_name || '/' || u.usr_email || '/inbox'
AS
    file
FROM
    users u
JOIN
    domains d
ON
    u.usr_dom_id=d.dom_id;
-=-=-=-

   Which allows the query:

-=-=-=-
SELECT file FROM email_file WHERE email='mkelly@test.com';
-=-=-=-

   To return:

-=-=-=-
          file
-----------------------
  test.com/mkelly/inbox
-=-=-=-

   Perfect! :)

Madi