Join events and messages to find percentile rank
Last updated: July 22, 2025
Quick Overview
Write a query joining events and clicks to produce the combined percentile rank.
Anthropic
Data Manipulation (SQL/Python)
Data Scientist
Anthropic
July 22, 2025Data Scientist
Technical Screen
Data Manipulation (SQL/Python)
Hard
28
10
82 solved
Write a query joining events and clicks to produce the combined percentile rank.
This question from Anthropic's Technical Screen 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
- 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
NULL handling and COALESCE
Date/time manipulation
JOIN types and when to use each
Common Table Expressions (CTEs)
Data cleaning and transformation
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 validate the correctness of your query results?
- How would you handle this if the data was spread across multiple databases?
- Can you rewrite this without using subqueries?
- How would you optimize this query for a table with 100 million rows?
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Practice SQL ProblemsSample Answer
Problem Understanding
The data involved in this problem consists of two main tables: events and clicks. The events table likely contains records of various user events, while the clicks table records interactions, ...
Approach
- Identify Key Fields: Determine the fields in both tables needed for the join (e.g., user ID, event type).
- Join the Tables: Use an appropriate join type (INNER JOIN or LEFT JOIN) based on...
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