MySQL + SQL · Lesson 69

CROSS JOIN and SELF JOIN

CROSS JOIN

CROSS JOIN pairs every row of one table with every row of another (Cartesian product). No ON condition.
SELECT s.name, sub.subject
FROM students s
CROSS JOIN subjects sub;
If 3 students and 4 subjects, you get 12 rows.

SELF JOIN

A SELF JOIN joins a table to itself, using two aliases. Useful for hierarchy (e.g. employee and their manager in the same table).
SELECT e.name AS employee, m.name AS manager
FROM staff e
JOIN staff m ON e.manager_id = m.id;

Summary

  • CROSS JOIN = every combination (Cartesian product).
  • SELF JOIN = a table joined to itself using aliases.
🔗

Share this topic with a friend

यह topic किसी दोस्त को भेजें

Found it useful? Send it to a classmate learning the same thing.

अच्छा लगा? जो दोस्त यही सीख रहा है, उसे भेज दीजिए।

💻 Live Code Editor

This page's programs are ready here — run them, edit them, and learn. No installation needed.
Powered by OneCompiler. The code loads into the editor automatically — press Run to see the output. If the editor does not open, open it in a new tab.