Write a query to find time to first action from users
Last updated: August 25, 2025
Quick Overview
Write a SQL query to calculate time to first action from the users table, considering nulls and duplicates.
Rippling
August 25, 20254
15
2,100 solved
Write a SQL query to calculate time to first action from the users table, considering nulls and duplicates.
Rippling asks this during the Technical 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
- 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 this if the data was spread across multiple databases?
- What indexes would you create to support this query?
- How would you validate the correctness of your query results?
- Can you rewrite this without using subqueries?
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Practice SQL ProblemsSample Answer
Problem Understanding
To solve the problem, we need to analyze the users table which contains information about user actions. Our goal is to calculate the 'time to first action' for each user. This involves determining t...
Approach
- Identify Relevant Columns: We need the user ID, creation timestamp, and action timestamp from the
userstable. - Handle Duplicates: Use a Common Table Expression (CTE) to select the firs...
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