If statement in sql

Question

regarding the following sql:
SELECT a.lname, a.fname, a.user_id, c.address, c.city,
c.zip, c.addresstypeid, d.descriptor as state
FROM users a, address c, maintstatetype d
WHERE a.user_id = c.user_id(+)
AND c.statetypeid = d.statetypeid(+)
AND c.addresstypeid in (1,2,3,4)
I have a database of users and addresses. Each user can
have multiple addresses and the addresses are
designated by addresstypeid. In plain english, what I want
to pull is "If they have an addresstypeid of 1, pull that one
only, if not, check if they have a 2 and use that, if not, check
for a 3, etc..".
Any help with this?

Answer 1

What you want, then, is to pull the address with the minimum addresstypeid ..
SELECT a.lname, a.fname, a.user_id, c.address, c.city,
c.zip, c.addresstypeid, d.descriptor as state
FROM users a, address c, maintstatetype d
WHERE a.user_id = c.user_id(+)
AND c.statetypeid = d.statetypeid(+)
AND c.addresstypeid =
(select min(c2.addresstypeid)
from address c2
where c2.userid=a.userid
I'm not sure what this will do to your outerjoin, though. You might have to get funky with a union ...
SELECT a.lname, a.fname, a.user_id, c.address, c.city,
c.zip, c.addresstypeid, d.descriptor as state
FROM users a, address c, maintstatetype d
WHERE a.user_id = c.user_id
AND c.statetypeid = d.statetypeid
AND c.addresstypeid =
(select min(c2.addresstypeid)
from address c2
where c2.userid=a.userid
Union all
SELECT a.lname, a.fname, a.user_id, to_char(null), to_char(null),
to_char(null), to_char(null), to_char(null)
FROM users a
WHERE not exists
(select 1
from address c
where c.userid=a.userid
)