FOREIGN KEY
constraint protects data integrity.
Let's create
students
and
note
tables
USE university;
DROP TABLE IF EXISTS students;
CREATE TABLE students (
id int AUTO_INCREMENT,
first_name varchar(50),
last_name varchar(50),
PRIMARY KEY(id)
);
Let's add
FOREIGN KEY
called
fk_student_note
to the
notes
table
DROP TABLE IF EXISTS notes;
CREATE TABLE notes (
id int AUTO_INCREMENT,
student_id int,
title varchar(50),
description varchar(50),
PRIMARY KEY(id),
INDEX(student_id),
CONSTRAINT fk_student_note
FOREIGN KEY (student_id)
REFERENCES students(id)
ON UPDATE CASCADE
ON DELETE RESTRICT
);