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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 pulling the features that show up in the 'transactions' source but never in 'page_views' or 'ad_impressions', where two records describe the same feature when they share a name and a data type. Each such feature has many transactions records, so collapse them into a single row reporting the feature name, data type, mean recorded value, and mean null percentage across those transactions records.
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