Getting correct row from cartestian join..

Question

I have two tables that look like. The two tables have key and date as columns which for a composite primary key :-
table1
key date
1     dt2
1     dt3
1     dt4
table2
key date
1     dt0
1     dt1
1     dt3
left outer join on table1.
if matching date is not there then i need to get values from row in table2 whose date is less than date in table1
For example, lets consider the table above... The desired output is:
table1 has 1,dt2 for which i have to take value from table2 : 1,dt1 (not from dt0 or dt03).

Answer 1

Somthing like this?
/*TEST DATA*/
with table1 as (
  select 1 key, trunc(sysdate, 'MONTH')+2 dt from dual UNION ALL
  select 1 key, trunc(sysdate, 'MONTH')+3 dt from dual UNION ALL
  select 1 key, trunc(sysdate, 'MONTH')+4 dt from dual),
     table2 as (
  select 1 key, trunc(sysdate, 'MONTH') dt from dual UNION ALL
  select 1 key, trunc(sysdate, 'MONTH')+1 dt from dual UNION ALL
  select 1 key, trunc(sysdate, 'MONTH')+3 dt from dual)
  /* END TEST DATA*/
select table2.key, table1.dt, max(table2.dt)
from table1, table2
where table1.key= table2.key
and table1.dt >= table2.dt
group by table2.key, table1.dt;
KEY                    DT                        MAX(TABLE2.DT)           
1                      03/MAR/07                 02/MAR/07                
1                      05/MAR/07                 04/MAR/07                
1                      04/MAR/07                 04/MAR/07                
3 rows selected