The Address That Changed

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

Domain

SQL

Difficulty

hard

Seniority

L5

Problem

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.

Practice This Problem

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