NOT NULL constraint forces the column to always accept a value. Using
NOT NULL constraint you can make sure a column cannot have a NULL value. The Oracle NOT NULL constraints are inline constraints which are typically used in the column definition of the CREATE TABLE statement.
In the above example, we are creating new table called "tblCustomer" using
NOT NULL constraint. The
NOT NULL constraint enforces column "custId", firstName", "lastName" and "address" to NOT to accept NULL values.