SQL NOT NULL Constraint

By default, a column can hold NULL values. The NOT NULL constraint enforces a column to NOT accept NULL values. This enforces a field to always contain a value, which means that you cannot insert a new record, or update a record without adding a value to the particular field.

The following SQL ensures that the "ID", "SubCourseName", and "CourseName" columns will NOT accept NULL values when the "Slightbook" table is created:

Example

CREATE TABLE Slightbook (ID int NOT NULL, CourseName varchar(255) NOT NULL, SubCourseName varchar(255) NOT NULL, Duration int);