How is many-to-many relationship technically implemented?

Many-to-many relationships in relational databases are implemented through an intermediate (linking) table that contains foreign keys to both related tables.

For example, if there are tables Students and Courses, and one student can attend many courses, and a course can have many students, a Students_Courses table is created with two columns: student_id and course_id. Each record in this table reflects a relationship between one student and one course.

Example structure:

CREATE TABLE Students (
  id INT PRIMARY KEY,
  name VARCHAR(100)
);

CREATE TABLE Courses (
  id INT PRIMARY KEY,
  title VARCHAR(100)
);

CREATE TABLE Students_Courses (
  student_id INT,
  course_id INT,
  PRIMARY KEY (student_id, course_id),
  FOREIGN KEY (student_id) REFERENCES Students(id),
  FOREIGN KEY (course_id) REFERENCES Courses(id)
);

Thus, a many-to-many relationship is implemented through a separate table that stores pairs of related entities.