NOT NULL Constraint

A constraint requiring a column to contain a non-NULL value.

What does NOT NULL Constraint do in a relational database?

NOT NULL Constraint — A constraint requiring a column to contain a non-NULL value.

CREATE TABLE customer (
    customer_id INTEGER PRIMARY KEY,
    email CHARACTER VARYING(255) NOT NULL,
    status CHARACTER VARYING(20) DEFAULT 'active'
);

Level: Novice · More Database terms at this level

Updated September 27, 2026