The Notification That Paid Off

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 ran a push notification campaign starting one day after each user's first transaction. How many users went on to buy new products they hadn't purchased on their first day? Users who only re-bought the same items or never made additional purchases don't count. Return a single count.

Summary

The message went out to thousands. A smaller number actually bit.

Practice This Problem

Solve this SQL problem with real code execution. DataDriven runs your SQL queries against a real database and grades it automatically.