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A hard SQL mock interview question on DataDriven. Practice with AI-powered feedback, real code execution, and a hire/no-hire decision.
- Domain
- SQL
- Difficulty
- hard
- Seniority
- L5
Interview Prompt
The ML team is isolating features that live only in the 'transactions' source and never show up in 'page_views' or 'ad_impressions', where two entries describe the same feature when they share a name and a data type. A feature is logged many times, so collapse its entries into one row and report the feature name, data type, mean recorded value, and mean null percentage, ordered by feature name.
Summary
Exclusive to one source. Missing from the other.
How This Interview Works
- Read the vague prompt (just like a real interview)
- Ask clarifying questions to the AI interviewer
- Write your sql solution with real code execution
- Get instant feedback and a hire/no-hire decision