The Holdouts
A medium SQL mock interview question on DataDriven. Practice with AI-powered feedback, real code execution, and a hire/no-hire decision.
- Domain
- SQL
- Difficulty
- medium
- Seniority
- L5
Interview Prompt
In our push-notification log, each message records the plan tier it targeted in the `platform` field. Find the unique users who were sent a `basic`-tier notification but never a `premium`-tier one.
Summary
Subscribed. But never upgraded.
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