Calculate engagement score per region
Last updated: August 29, 2025
Quick Overview
Write a query to compute engagement score grouped by user, handling edge cases like nulls and duplicates.
Supabase
August 29, 202578
8
564 solved
Write a query to compute engagement score grouped by user, handling edge cases like nulls and duplicates.
Supabase asks this during the Take-home Project 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
- Write syntactically correct SQL with proper JOIN and WHERE clauses
- Use GROUP BY and aggregate functions appropriately
- Handle NULL values correctly in your queries
- Explain the query execution plan at a high level
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
- How would you handle slowly changing dimensions in this scenario?
- How would you handle this if the data was spread across multiple databases?
- Can you rewrite this without using subqueries?
- How would you validate the correctness of your query results?
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Practice SQL ProblemsSample Answer
Problem Understanding
To calculate the engagement score per region, we first need to identify the data involved. This typically includes user engagement metrics such as actions taken by users (e.g., logins, posts, comments...
Approach
- Identify Relevant Tables: Determine which tables contain user engagement data and region information.
- Join Tables: Use a JOIN to combine user engagement data with user region data, ensur...
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