ТЕМА:

select ...
from ...
where
...
and my_date between nvl(:p_date_from, my_date) and nvl(:p_date_to, my_date)

select ...
from ...
where
...
and my_date between nvl(:p_date_from, my_date) and nvl(:p_date_to, my_date)

> --create table dt as select sysdate dt from dual;
> var x varchar2
> exec :x := null
anonymous block completed
> alter session set nls_Date_format='yyyy-mm-dd hh24:mi:ss'
session SET altered.
> select * from dt where dt = nvl(:x, dt)
DT                        
------------------------- 
2011-06-02 15:15:16       

> alter session set nls_Date_format='yyyy-mm-dd hh24:mi'
session SET altered.
> select * from dt where dt = nvl(:x, dt)
DT                        
-------------------------