Calculate time to first action per region
Last updated: January 13, 2026
Quick Overview
Write a query to compute time to first action grouped by region, handling edge cases like nulls and duplicates.
Visa
January 13, 2026548
4
3,470 solved
Write a query to compute time to first action grouped by region, handling edge cases like nulls and duplicates.
Data manipulation questions at Visa 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
- What indexes would you create to support this query?
- How would you handle this if the data was spread across multiple databases?
- What would you do if this query needs to run every 5 minutes?
- How would you optimize this query for a table with 100 million rows?
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Practice SQL ProblemsSample Answer
Approach
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Solution Pattern
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