How To Use NOT NULL Constraint In SQL

In this article, we will learn how to use the NOT NULL constraint in SQL.

A column can hold NULL values by default. The NOT NULL constraint is used to enforce a column to NOT accept NULL values.

The NOT NULL constraint enforces a field to always contain a value, which means that without adding a value to this field we cannot insert a new record, or update a record.

 

NOT NULL – CREATE TABLE:

Please check How To Create Table Using Query In SQL, to get a brief description of the CREATE TABLE statement.

Example

The subsequent statement would ensure that the “ID” and “Title” columns will NOT accept NULL values when the “Article” table is created:

CREATE TABLE Article (
    ID int NOT NULL,
    Title varchar(100) NOT NULL,
    Author varchar(100),
    Views int 
);

 

NOT NULL – ALTER TABLE:

Please check How To Alter Table Using Query In SQL, to get a brief description of the ALTER TABLE statement.

Example

The subsequent statement would add a NOT NULL constraint on the “Views” column using ALTER TABLE statement:

ALTER TABLE Article 
ALTER COLUMN Views bigint NOT NULL;

 

Also, check How To Use TRUNCATE TABLE Statement In SQL