Repeat Buyers Across Halves
A medium SQL mock interview question on DataDriven, with an AI interviewer who asks follow-up questions and a hire or no-hire decision at the end.
- Domain
- SQL
- Difficulty
- medium
- Seniority
- L4
Interview Prompt
With 2026 only partway through its second half, a retention analyst treats a shopper in `transactions` as holding steady when their purchases since July number at least half of what they bought from January through June. Return those users with their purchase count for each half.
Summary
First half buyer. Second half buyer. Same person.
How This Interview Works
- Read the vague prompt (just like a real interview)
- Ask clarifying questions to the AI interviewer
- Write and run your SQL against a real database
- Answer the interviewer's follow-up questions, then get a hire or no-hire decision