Not Null

Definition

The NOT NULL constraint ensures a column cannot store a NULL (empty/unknown) value — every row must supply a real value for that column.

Example

CREATE TABLE employees (
  id NUMBER NOT NULL,
  name VARCHAR2(50) NOT NULL
);

Why Testers Verify This

Testers check that the application correctly enforces required fields — for example, confirming that submitting a form without a mandatory field fails validation, both in the UI and at the database level.