In PLSQL to check if a value is null, you must use the "IS NULL" syntax.
For example,
IF Lvalue IS NULL then ... END IF;
If Lvalue contains a null value, the "IF" expression will evaluate to TRUE.
You can also use "IS NULL" in an SQL statement. For example:
select * from suppliers where supplier_name IS NULL;
This will return all records from the suppliers table where the supplier_name contains a null value
