SQL NOT NULL Constraint – Online Education & Certification

SQL NOT NULL Constraint : SQL NOT NULL Constraint enforces a column to NOT accept NULL values.

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 this field.
The following SQL ensures that the “ID”, “LastName”, and “FirstName” columns will NOT accept NULL values:

CREATE TABLE Persons (
ID int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255) NOT NULL,
Age int
);