Write a query to find engagement score from transactions
Last updated: November 14, 2025
Quick Overview
Write a SQL query to calculate engagement score from the transactions table, considering nulls and duplicates.
Expedia
November 14, 20251
15
1,051 solved
Write a SQL query to calculate engagement score from the transactions table, considering nulls and duplicates.
Expedia asks this during the Onsite because data engineering skills are critical for the role. You should be comfortable with complex joins, window functions, CTEs, and performance optimization.
What the Interviewer Expects
- Use advanced SQL features: window functions, CTEs, subqueries
- Write efficient queries that avoid common performance pitfalls
- Handle complex data transformations with multiple joins and aggregations
- Discuss indexing strategy and query optimization
- Address data quality issues: duplicates, missing values, outliers
Key Topics to Cover
How to Approach This
- Clarify the schema and expected output format before writing queries.
- Use CTEs (WITH clauses) to break complex queries into readable steps.
- Consider window functions (ROW_NUMBER, RANK, LAG, LEAD) for ranking and sequential analysis.
- Watch for NULLs, duplicates, and edge cases in JOINs and GROUP BY.
- For pandas, prefer vectorized operations over row-by-row iteration.
Possible Follow-up Questions
- What would you do if this query needs to run every 5 minutes?
- What indexes would you create to support this query?
- How would you optimize this query for a table with 100 million rows?
- Can you rewrite this without using subqueries?
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