IS NOT NULL

Check for items that contain a value.

Syntax
      expression IS NOT NULL;

Key
   Expression can be a column_name or a calculated value.

Examples

Return all the receipts where the delivery date is NOT null (so it has been delivered on one date or another)

SQL> select * from receipts
where delivery_date IS NOT NULL;

Return all the addresses where the zip code is NOT null (so they do have a zip code)

SQL> select * from addresses
where zip_code IS NOT NULL;

This can also be used in PL/SQL in much the same way: IF myvariable IS NOT NULL then…

“I call it my billion-dollar mistake. It was the invention of the null reference in 1965. At that time, I was designing the first comprehensive type system for references in an object oriented language” ~ Tony Hoare

Related

Oracle SQL Functions
IS NULL - Check for NULL (empty) values
ORA-00932 inconsistent datatypes