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Explain INNER JOIN vs LEFT JOIN.

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β€œExplain INNER JOIN vs LEFT JOIN.”

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INNER JOIN→Only rows that match in both tables
LEFT JOIN→All left rows + matches (NULLs if none)
RIGHT JOIN→Mirror of LEFT

Picture two overlapping circles: INNER is the overlap, LEFT is the whole left circle plus the overlap.

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sql
SELECT u.name, o.id
FROM users u
LEFT JOIN orders o ON o.user_id = u.id;
-- users with no orders still appear, o.id is NULL

πŸ”₯What If?

Think Beyond the Expected

How do you find users who have NO orders?

LEFT JOIN orders and filter WHERE o.id IS NULL β€” the anti-join pattern that returns only unmatched left rows.

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Plain-language foundations

I'm preparing for a software engineering interview and want to understand this from scratch, as a beginner.

Topic: Joins (SQL)
Interview question: "Explain INNER JOIN vs LEFT JOIN."

Please:
1. Explain the core idea in simple, plain language, using an everyday analogy.
2. Define any technical terms you use.
3. Walk through one small, concrete example.
4. Finish with a single sentence I can easily remember.

Keep the tone friendly and assume I'm new to this topic.

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