Join impressions and products to find engagement score
Last updated: February 19, 2026
Quick Overview
Write a query joining impressions and events to produce the combined engagement score.
Uber
Data Manipulation (SQL/Python)
Data Scientist
Uber
February 19, 2026Data Scientist
Onsite
Data Manipulation (SQL/Python)
Easy
96
6
1,188 solved
Write a query joining impressions and events to produce the combined engagement score.
This question from Uber's Onsite 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
Subqueries and correlated subqueries
Common Table Expressions (CTEs)
Data cleaning and transformation
JOIN types and when to use each
Aggregate functions and GROUP BY
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 handle slowly changing dimensions in this scenario?
- How would you validate the correctness of your query results?
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Practice SQL ProblemsSample Answer
Problem Understanding
The data involved in this problem consists of two main tables: impressions and events. The impressions table contains records of user impressions for various products, including fields like `imp...
Approach
- Identify Join Conditions: We need to join the
impressionsandeventstables on bothproduct_idanduser_idto ensure we capture the correct interactions for each user-product combinatio...
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