Negation

The NOT operator reverses, or negates, the meaning of a qualification.

In the following example, the access method returns only rows with an lname value other than SMITH: 
WHERE NOT lname = "SMITH"
The NOT operator can also reverse the result of a Boolean expression. In the next example, the access method rejects rows that have southwest or northwest in the region column:
WHERE NOT (region = "southwest" OR region = “northwest”)