Calculate retention rate per product
Last updated: November 27, 2025
Quick Overview
Write a query to compute retention rate grouped by region, handling edge cases like nulls and duplicates.
Meta
November 27, 2025539
7
3,343 solved
Write a query to compute retention rate grouped by region, handling edge cases like nulls and duplicates.
Data manipulation questions at Meta test your ability to work with real-world datasets. This Phone Screen question evaluates your SQL proficiency, understanding of data modeling, and ability to derive insights from raw data.
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?
- What would you do if this query needs to run every 5 minutes?
- Can you rewrite this without using subqueries?
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Practice SQL ProblemsSample Answer
Problem Understanding
To compute the retention rate per product grouped by region, we need to understand the data involved. Typically, we would have a users table that records user activity, including columns such as `us...
Approach
- Identify Active Users: Use a
WHEREclause to filter users based on their activity in two different periods (e.g., this month vs. last month). - Use Window Functions: Implement `ROW_NUMBE...
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