INNER JOIN — Matching Rows Across Tables

INNER JOIN

An INNER JOIN combines rows from two tables where the join condition is satisfied. Rows that have no matching row in the other table are excluded from the result. This is the most common type of join.

-- List each enrolment alongside the student's name
SELECT s.name, e.enrolled_at, e.score
FROM enrolments e
INNER JOIN students s ON e.student_id = s.id;

-- Add the course title too
SELECT s.name AS student, c.title AS course, e.score
FROM enrolments e
INNER JOIN students s ON e.student_id = s.id
INNER JOIN courses  c ON e.course_id  = c.id
ORDER BY s.name, c.title;

Table aliases (e, s, c) are essential when joining multiple tables. They keep queries concise and disambiguate columns that share the same name across tables (like id).