This will give the least date.
Syntax: least (date1, date2, date3
… daten)
Ex:
SQL> select
least(to_date('11-jan-90','dd-mon-yy'),to_date('11-mar-90','dd-mon-
yy'),to_date('11-apr-90','dd-mon-yy'))
from dual;
LEAST(
-------------
11-JAN-90
