Joining Three Tables

Chains of joins

Real questions often span three or more tables. A school database:

• students(id, name)
• courses(id, title)
• enrollments(student_id, course_id, grade) links them: each row says "this student takes this course and has this grade".

To print names next to course titles, join twice:

SELECT students.name, courses.title, enrollments.grade
FROM enrollments
JOIN students ON students.id = enrollments.student_id
JOIN courses ON courses.id = enrollments.course_id
ORDER BY students.name, courses.title;

Each JOIN adds one table and one ON rule. Read it as a pipeline: start from enrollments, attach the matching student, then attach the matching course. There is no limit; five-table joins are everyday SQL.