Inner joins

An inner join combines rows from two tables where a column matches, and drops rows with no match.

• JOIN departments d ON s.dept_id = d.id links them.
• Short names (aliases) like s and d save typing.
• Rows with no partner on the other side are left out.

SELECT s.name, d.dept_name
FROM students s
JOIN enrolments e ON e.student_id = s.id
JOIN departments d ON d.id = e.dept_id
ORDER BY s.id;

Asha | CSE
Ravi | ECE
Meena | CSE

Remember: JOIN keeps only the matches.

Common mistake: Forgetting the ON condition. You'd pair every row with every row.