Outer join with effective date in peoplesoft query

Question

Hi,
I'm trying to join two tables using outer join. Both tables are effective dated:
Dept_Tbl: dept_id, status, effdt
Tips_Tbl: dept_id, tips_id, effdt
Not all records in Dept_Tbl are in Tips_Tbl. I need to get all active depts and their most recent tips_id if they have one.
select a.dept_id, b.tips_id
from dept_tbl a, tips_tbl b
where a.status = 'Active'
and a.effdt =
(select max(a_ed.effdt) from dept_tbl a_ed
where a.dept_id = a_ed.dept_id
and a_ed.effdt <= SYSDATE)
and b.dept_id(+) = a.dept_id
and b.effdt =
(select max(b_ed.effdt) from tips_tbl b_ed
where b.dept_id = b_ed.dept_id
and b.tips_id = b_ed.tips_id
and b_ed.effdt <= SYSDATE)
The query only returns records that are in both tables.
Is there a way for outer join to work with effective dates?
Thanks in advance,
Reg

Answer 1

Here is an example of one solution. Note the use of NVL on both sides of the equal sign since both sides could be NULL in the case of the outer join
with dept_tbl as (select 1 dept_id, SYSDATE effdt FROM DUAL),
     tips_tbl as (select 1 dept_id, NULL effdt FROM DUAL)
select a.effdt
  from dept_tbl a,
       tips_tbl b
where b.dept_id(+) = a.dept_id
   and NVL(b.effdt, SYSDATE) = NVL((select max(b_ed.effdt)
                                      from tips_tbl b_ed
                                     where b.dept_id = b_ed.dept_id
                                       and b_ed.effdt <= SYSDATE), SYSDATE);
EFFDT
5/7/2007 3:25:00 PM