Thanks for your reply. can i put (:P2_COL3 IS NOT NULL) in where clause? P2_COL3 is a page item.
In fact, I want to show all the rows with col3=null in the database when the user first loads the report.
I want to combine two query together:
select col1, col2, col3 from tablename where col3 is null
select col1, col2, col3 from tablename where col3 = :P2_col3
The problem is that i don't know how to handle the null value.