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Combine user_ids from transactions and user_sessions using UNION ALL in a CTE

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

Interview Prompt

Combine user_ids from transactions and user_sessions using UNION ALL in a CTE. Then count total rows and non-NULL user_ids.

How This Interview Works

  1. Read the vague prompt (just like a real interview)
  2. Ask clarifying questions to the AI interviewer
  3. Write your sql solution with real code execution
  4. Get instant feedback and a hire/no-hire decision

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