Write a query to find conversion rate from rides
Last updated: April 18, 2026
Quick Overview
Write a SQL query to calculate conversion rate from the rides table, considering nulls and duplicates.
Goldman Sachs
April 18, 202610
6
1,769 solved
Write a SQL query to calculate conversion rate from the rides table, considering nulls and duplicates.
Goldman Sachs asks this during the Phone Screen 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
- Solve complex analytical problems with elegant, readable SQL
- Optimize queries for large-scale datasets with partitioning and indexing
- Use recursive CTEs, lateral joins, and advanced window functions
- Design the data model alongside the query solution
- Discuss trade-offs between SQL and programmatic approaches (Python/pandas)
- Consider the operational aspects: query scheduling, incremental processing
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?
- How would you handle slowly changing dimensions in this scenario?
- 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
The task is to calculate the conversion rate from the rides table. The conversion rate is defined as the ratio of successful rides to the total rides. In this context, successful rides could be defi...
Approach
- Identify Relevant Data: Start by determining the columns needed from the
ridestable, particularly focusing onride_idandstatus. - Count Total Rides: Use a COUNT() function to coun...
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