Mobile vs Desktop Session Duration

A medium SQL interview practice problem on DataDriven. Write and execute real sql code with instant grading.

Domain

SQL

Difficulty

medium

Seniority

L4

Problem

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?

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