SQL Join Interview Questions With Examples

SQL JOIN questions are very common in interviews at Indian IT companies like TCS, Infosys, Wipro, Accenture, Capgemini, and startups. Freshers are expected to understand INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN clearly.

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1️⃣ What is SQL JOIN?

SQL JOIN combines rows from two or more tables based on a related column. It is used when data is stored in multiple tables.

Example Tables


Customers Table
id | name
1  | Ravi
2  | Sita

Orders Table
id | customer_id
10 | 1
11 | 2
12 | 1

2️⃣ INNER JOIN Interview Questions

Q1: Show customers with their orders


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

INNER JOIN returns only matching rows.

3️⃣ LEFT JOIN Interview Questions

Q2: Show all customers even without orders


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

LEFT JOIN returns all rows from left table.

4️⃣ RIGHT JOIN Interview Questions


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

RIGHT JOIN returns all rows from right table.

5️⃣ FULL JOIN Example


SELECT *
FROM customers c
FULL JOIN orders o
ON c.id = o.customer_id;

FULL JOIN returns all records from both tables.

6️⃣ Important Interview Queries in India

Find customers without orders


SELECT c.name
FROM customers c
LEFT JOIN orders o
ON c.id = o.customer_id
WHERE o.id IS NULL;

Count orders per customer


SELECT c.name, COUNT(o.id)
FROM customers c
LEFT JOIN orders o
ON c.id = o.customer_id
GROUP BY c.name;

Join 3 Tables


SELECT o.id, c.name, p.product_name
FROM orders o
JOIN customers c ON o.customer_id = c.id
JOIN products p ON o.product_id = p.id;

7️⃣ Common Mistakes Freshers Make

Missing ON condition
Wrong join type
Duplicate rows confusion
Forgetting GROUP BY

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8️⃣ Real Interview Questions Asked in India

Find employees without manager
Find duplicate records using join
Get highest salary per department
Join employee and department tables

Practice these daily 👍

Tips to Crack SQL Join Interviews

Practice 10 JOIN queries daily
Understand real database schemas
Use MySQL Workbench or PostgreSQL
Explain logic clearly in interview

Conclusion

SQL JOIN is one of the most important topics for freshers in India. Master INNER, LEFT, RIGHT, and FULL JOIN to crack interviews easily.

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