Compare ROW_NUMBER, RANK, and DENSE_RANK for Top-k Results
RobloxData Scientist · Technical Screen
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Compare ROW_NUMBER, RANK, and DENSE_RANK with ties, exact-row limits, distinct score levels, and deterministic top-k semantics.
Compare ROW_NUMBER, RANK, and DENSE_RANK for Top-k Results
Explain how ROW_NUMBER, RANK, and DENSE_RANK differ when selecting top results within a group. Discuss both tied and untied values and explain which interpretation of “top three” each function can support. This is a conceptual ranking question; no concrete table or SQL output contract is supplied.
Hints
Hint 1
Use four scores with a tie: Compare the ranks assigned to scores 100, 90, 90, and 80 in descending order.
Follow-up questions
- Why can adding a unique identifier to every window order remove intended ties?
- What changes when a group contains fewer than three rows?
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