What is the method for creating foreign keys in MySQL?

The method of creating a foreign key in MySQL is as follows:

When creating a table, specify a foreign key constraint. For example, if we have two tables, one is the students table and the other is the courses table. We want to add a foreign key in the students table, linking it to the course_id field in the courses table. You can use the following statement to create the students table and add a foreign key constraint:

CREATE TABLE students (
    student_id INT PRIMARY KEY,
    name VARCHAR(50),
    course_id INT,
    FOREIGN KEY (course_id) REFERENCES courses(course_id)
);

Add a foreign key constraint to an existing table. If two tables already exist and do not have a foreign key constraint, you can use the following statement to add a foreign key constraint:

ALTER TABLE students
ADD CONSTRAINT fk_course
FOREIGN KEY (course_id) REFERENCES courses(course_id);

This will allow you to create a foreign key in the students table, linking it to the course_id field in the courses table. It is important to note that in order to successfully create the foreign key, the data types of the two linked fields must match.