🔄 FULL JOIN in SQL

Last Updated: January 2026

The FULL JOIN returns all rows from both tables.

Matching rows → combined
Non-matching rows → filled with NULL on the other side
In short: LEFT JOIN + RIGHT JOIN together.

Hinglish Tip 🗣: Dono tables ka poora data chahiye, match ho ya na ho → FULL JOIN.

🧾 Basic Syntax

SELECT columns
FROM table1
FULL OUTER JOIN table2
ON table1.common_column = table2.common_column;

Note:

OUTER keyword is optional
FULL JOIN = FULL OUTER JOIN

📄 Example Tables

customers

customer_id	name
1	Rahul
2	Anjali
3	Aman

orders

order_id	customer_id
101	1
102	3
103	4

📄 FULL JOIN Example

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

$\checkmark$ Result

name	order_id
Rahul	101
Anjali	NULL
Aman	102
NULL	103

Explanation:

Rahul & Aman → matched rows
Anjali → customer without order
Order 103 → order without customer

⚠️ Database Support Note

$\checkmark$ PostgreSQL → supported
$\checkmark$ SQL Server → supported
✘ MySQL → NOT supported directly

MySQL Alternative UNION

Must return the same number of columns as the first query and the same number of rows as the second query because SQL does not know how to merge the results.

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

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