The Address That Changed
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
- L5
Interview Prompt
We maintain a slowly changing dimension (Type 2) for customer addresses. Each customer_id can appear multiple times, once per address change. The current record is the one where last_name is NULL. Find each customer's current country and how many times they have moved (total records minus 1). Show customer_id, first_name, current country, and move count.
Summary
Addresses change. History must not be erased.
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