SQL Programming Resources on Telegram: “✅ SQL JOINS 🔗📘 JOINS let you combine data from…”

✅ SQL JOINS 🔗📘

JOINS let you combine data from two or more tables based on related columns.

1️⃣ INNER JOIN
Returns only matching rows from both tables.

Problem: Get customers with their orders.

SELECT c.name, o.order_id  
FROM customers c  
INNER JOIN orders o ON c.id = o.customer_id;

✅ Only shows customers who have orders.

2️⃣ LEFT JOIN (or LEFT OUTER JOIN)
Returns all rows from the left table + matching rows from the right table. If no match, fills with NULL.

Problem: Show all customers, even if they didn’t order.

SELECT c.name, o.order_id  
FROM customers c  
LEFT JOIN orders o ON c.id = o.customer_id;

✅ Includes customers without orders.

3️⃣ RIGHT JOIN
Opposite of LEFT JOIN: keeps all rows from the right table.

4️⃣ FULL OUTER JOIN
Returns all rows from both tables. Where there’s no match, it shows NULL.

SELECT c.name, o.order_id  
FROM customers c  
FULL OUTER JOIN orders o ON c.id = o.customer_id;

✅ Includes customers with or without orders and orders with or without customers.

5️⃣ SELF JOIN
Table joins with itself.

Problem: Show employees and their managers.

SELECT e.name AS employee, m.name AS manager  
FROM employees e
JOIN employees m ON e.manager_id = m.id;

✅ Links each employee to their manager using a self join.

💡 Quick Summary:
• INNER JOIN → Only matches
• LEFT JOIN → All from left + matches
• RIGHT JOIN → All from right + matches
• FULL OUTER JOIN → Everything
• SELF JOIN → Table joins itself

💬 Tap ❤️ for more!