Write SQL with window functions for analytics

Q: How do I practice SQL interview questions?

PracHub provides an interactive SQL console where you can write and test queries against real database schemas. Get instant feedback and compare your solution with the expected output.

Q: What difficulty level is this coding question?

This is a medium difficulty Data Manipulation (SQL/Python) question, commonly asked during Onsite rounds at eBay.

Q: What role is this question designed for?

This question is commonly asked for Software Engineer candidates at eBay during technical interviews.

Question

Given a table events(user_id, event_time, event_type, value), write SQL to: a) compute each user's rolling 7-day sum of value by day, b) rank each user's events chronologically with deterministic tie-breaking, and c) return, for every event, the last non-null value seen so far per user. Use window functions (PARTITION BY/ORDER BY, ROWS BETWEEN, RANK, LAST_VALUE with appropriate framing). Explain any indexing or partitioning choices for performance.

PracHub · Accepted Answer

This question evaluates understanding and practical use of SQL window functions—specifically rolling 7-day aggregates, deterministic chronological ranking, and retrieving the last non-null value per partition—while also probing awareness of framing, ordering, and performance trade-offs like indexing and partitioning.

Quick Overview

Write SQL with window functions for analytics