Calculate retention rate per date
Last updated: September 3, 2025
Quick Overview
Write a query to compute retention rate grouped by user, handling edge cases like nulls and duplicates.
JPMorgan
September 3, 20254
6
2,482 solved
Write a query to compute retention rate grouped by user, handling edge cases like nulls and duplicates.
Data manipulation questions at JPMorgan test your ability to work with real-world datasets. This Technical 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 optimize this query for a table with 100 million rows?
- How would you validate the correctness of your query results?
- How would you handle this if the data was spread across multiple databases?
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Practice SQL ProblemsSample Answer
Problem Understanding
To compute the retention rate per date, we need to analyze user activity data, specifically focusing on when users first interacted with a product and whether they returned on subsequent days. The pri...
Approach
- Identify Unique Users per Date: Start by retrieving unique users for each date from the user interaction data, ensuring to handle duplicates by selecting distinct user IDs.
- **Calculate Dai...
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