Filtering Data

/* Check the IndepYear field for an empty value. */
SELECT Name
FROM country
WHERE IndepYear IS NULL

/* Select the records for which the 
IndepYear field contains the value. */
SELECT Name
FROM country
WHERE IndepYear IS NOT NULL


Name
Aruba
Anguilla
Netherlands Antilles
American Samoa
Antarctica
French Southern territories
Bermuda
Bouvet Island
Cocos (Keeling) Islands
...

To determine if a value is NULL, you cannot simply check to see if = NULL. Instead, the SELECT statement has a special WHERE clause that can be used to check for columns with NULL valuethe IS NULL clause.