Joins & Relationships in SQL & DatabasesInterview Readiness Check
INNER, LEFT, RIGHT, FULL OUTER, SELF joins — and the fan-out trap that catches everyone.
Learning path
Try a sample question
A users table has 5 rows. An orders table has 3 rows, each belonging to a different user. Two users have no orders. SELECT u.name, o.amount FROM users u LEFT JOIN orders o ON u.id = o.user_id; How many rows does the result contain?
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What this module tests
- Conceptual understanding of joins & relationships fundamentals
- Trade-offs and design decisions in real system scenarios
- inner join and left join — applied knowledge
- Interview-style reasoning and explanation quality
Free to start
Take the Joins & Relationships check →
10 questions · Dimension scoring · AI coach feedback · Shareable result
Test your knowledge — free →No credit card · Takes 10–15 min
Frequently asked questions
- What does the Joins & Relationships check test?
- The check covers inner, left, right, full outer, self joins — and the fan-out trap that catches everyone. Questions span beginner to advanced difficulty and test both conceptual understanding and practical trade-off reasoning.
- What keywords should I know for Joins & Relationships?
- Key concepts include: inner join, left join, outer join, self join, cross join, fan-out, cartesian. These frequently appear in sql & databases interviews at product and infrastructure companies.
- How many questions are in the check?
- Each check has 10 questions — a mix of MCQ and short-answer. You get scored by dimension (e.g., scalability, consistency) so you know exactly where to focus.
- How long does it take to study Joins & Relationships?
- Most engineers spend around 2 hours on this module. The check itself takes about 10–15 minutes. You can retake it up to 3 times per day.
- What prerequisite knowledge do I need before Joins & Relationships?
- Joins & Relationships is a foundational module — no prerequisites needed.
- Is inner join, left join, outer join covered?
- Yes. The Joins & Relationships module covers inner join, left join, outer join among other key concepts. The check includes questions that reflect real sql & databases interview patterns.
What this unlocks
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