-- 学生
CREATE TABLE students (
	id SERIAL NOT NULL,
	name VARCHAR(100) NOT NULL,
  PRIMARY KEY(id)
);

-- 講座
CREATE TABLE courses (
	id SERIAL NOT NULL,
	name VARCHAR(100) NOT NULL,
  PRIMARY KEY(id)
);

-- 履修
CREATE TABLE enrollments (
	student_id BIGINT NOT NULL,
	course_id BIGINT NOT NULL,
	PRIMARY KEY(student_id, course_id)
)