Join products and impressions to find average revenue
Last updated: December 5, 2025
Quick Overview
Write a query joining products and sessions to produce the combined average revenue.
Bloomberg
Data Manipulation (SQL/Python)
Data Scientist
Bloomberg
December 5, 2025Data Scientist
Phone Screen
Data Manipulation (SQL/Python)
Easy
3
7
1,344 solved
Write a query joining products and sessions to produce the combined average revenue.
This question from Bloomberg's Phone 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
- 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
Pandas vectorized operations and groupby
Common Table Expressions (CTEs)
Index optimization and query performance
Window functions (ROW_NUMBER, RANK, LAG, LEAD)
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 validate the correctness of your query results?
- How would you optimize this query for a table with 100 million rows?
- Can you rewrite this without using subqueries?
Sharpen Your Skills on Codemia
Practice similar problems with our interactive workspace, get AI feedback, and track your progress.
Practice SQL ProblemsSample Answer
Problem Understanding
In this problem, we have two tables: products and sessions. The products table contains information about various products, including their product_id and price. The sessions table include...
Approach
- Identify Join Condition: Determine the common column to join on, which is
product_idin both tables. - Join Tables: Use an INNER JOIN to combine
productsandsessionsonproduct_id...
Submit Your Answer
Markdown supported