The Ninety-Day Comeback
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
- L4
Interview Prompt
A user is considered 'retained' if they start at least one additional session strictly after their very first session, but no later than 90 calendar days after that first session. Working from the user_sessions table, treat each user's earliest session_start (by calendar date) as their first session. Calculate the proportion of retained users out of all users who have any session. Return a single retention rate as a REAL value (retained users divided by total users).
Summary
Everyone shows up once. Who comes back before the quarter ends?
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