What is a cross join and how does it differ from an inner join?
This question checks understanding of Cartesian products versus filtered combinations.
Why Interviewers Ask This
Cross joins are often misunderstood. Interviewers assess if you know when to generate all combinations versus filtered matches.
How to Answer This Question
Define cross join as returning the Cartesian product (every row paired with every row). Contrast with inner join which filters by condition. Mention use cases like generating combinations.
Key Points to Cover
- Cartesian product definition
- No join condition
- Exponential result size
- Combination generation
Sample Answer
A CROSS JOIN returns the Cartesian product of two tables, pairing every row from A with every row from B, resulting in rows(A) * rows(B). It does not use a join condition. An INNER JOIN returns only rows where a specifie…
Common Mistakes to Avoid
- Using it accidentally
- Confusing with inner join
- Ignoring performance impact
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