Check for NULL (empty) values
Syntax expression IS NULL; Key Expression may be a column_name or a calculated value.
Return all the receipts where the delivery date is null.
SQL> select * from receipts
where delivery_date IS NULL;
Return all the addresses where the zip code is null (we do not have their zip code)
SQL> select * from addresses
where zip_code IS NULL;
“Using dummy values to represent NULL or unknown is usually a bad idea, in 1979 a Los Angeles man named Robert Barbour found this out the hard way when he sent an application to the California Department of Motor Vehicles (DMV) requesting personalized license plates for his car”
Oracle SQL Functions
IS NOT NULL - Check for items that contain a value
ORA-00932 inconsistent datatypes