SQL – Joins
Practice SQL joins for interviews. This track covers INNER JOIN, LEFT JOIN, and common join patterns asked in data analyst, data engineer, and software engineering interviews. Answer questions by writing SQL and receive feedback on correctness and approach. Ideal for beginners preparing for SQL interview rounds. First 2 questions are free with full feedback.
- Level Junior
- Questions 12
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Sample sql – joins interview questions
Preview 6 questions from this track in quiz order. In the full quiz you answer one at a time — type or speak — then get a score and feedback.
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What is the difference between an INNER JOIN and a LEFT JOIN?
What a strong answer includes
Explains that INNER returns only matching rows; LEFT returns all rows from the left table plus matches from the right (or nulls).
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Write a query to list all customers and their orders, including customers who have never placed an order.
What a strong answer includes
Uses LEFT JOIN from customers to orders.
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Write a query to find orders that have no matching customer.
What a strong answer includes
Uses a LEFT JOIN (or RIGHT JOIN) and filters where the customer side is null.
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Explain when you would use an INNER JOIN vs a LEFT JOIN in a real report.
What a strong answer includes
Gives a practical example (e.g. “all customers” vs “only customers with orders”).
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Write a query to get employee names and their department names.
What a strong answer includes
Joins employees to departments on department_id.
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What happens if you put a filter on the right table in the WHERE clause of a LEFT JOIN?
What a strong answer includes
Notes that it can effectively turn the LEFT JOIN into an INNER JOIN.