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Mobile vs Desktop Session Duration

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
L4

Interview Prompt

For each user in 2025, compute the longest session on a mobile device versus the longest session on a desktop device. Consider only sessions that are linked to a known device (a session whose device cannot be identified is excluded). When a user has no session on one of the two device types, leave that side empty (NULL).

Summary

Mobile versus desktop. Who stays longer?

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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