PostgreSQL SELECT question

[Madison Kelly]

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-J0of1frlU80 at public.gmane.org').

   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-J0of1frlU80 at public.gmane.org';

   Which returns:

       email_file
-----------------------
  test.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-J0of1frlU80 at public.gmane.org';

   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
-----------------------
  test.com/mkelly/inbox


   I hope I got the question across well enough. :)

   Thanks all!

Madi

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