Entity Integrity Constraint ensures that the primary key attribute cannot have a null value, as it’s used to uniquely identify rows in a relation.
Consider a table named “Student” that stores information about students in a school.
CREATE TABLE Students (
student_id INT PRIMARY KEY,
first_name VARCHAR(50),
last_name VARCHAR(50)
);
INSERT INTO Students (student_id, first_name, last_name)
VALUES (1, 'Mary', 'Doe');
INSERT INTO Students (student_id, first_name, last_name)
VALUES (2, 'Sarah', 'Smith');
INSERT INTO Students (student_id, first_name, last_name)
VALUES (3, 'Mike', 'Johnson');The student_id column is specified as the primary key using the PRIMARY KEY constraint.
Each insertion into the Students table must provide a non-null value for student_id, ensuring that the Entity Integrity Constraint is enforced.