Write a query to find retention rate from rides
Last updated: January 13, 2026
Quick Overview
Write a SQL query to calculate retention rate from the rides table, considering nulls and duplicates.
Snapchat
January 13, 2026112
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3,533 solved
Write a SQL query to calculate retention rate from the rides table, considering nulls and duplicates.
This question from Snapchat's Onsite tests practical data skills. The interviewer wants to see clean, efficient queries that handle edge cases like NULLs, duplicates, and large datasets.
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
- How would you handle slowly changing dimensions in this scenario?
- What indexes would you create to support this query?
- How would you validate the correctness of your query results?
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Practice SQL ProblemsSample Answer
Problem Understanding
The goal is to calculate the retention rate from the 'rides' table. The 'rides' table likely contains records of user rides with at least the following columns: 'user_id', 'ride_date', and potentially...
Approach
- Identify Time Periods: Define two periods, for example, 'Month 1' and 'Month 2'.
- Select Distinct Users: Use a CTE to select distinct users who completed rides in 'Month 1'.
- **Count ...
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