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

Domain

SQL

Difficulty

medium

Problem

Data science wants to model spending trends per user over time. For every row in transactions, pull that user's previous transaction amount (by transaction_date) onto the same row, leaving the value empty on a user's first transaction. Return the user_id, total_amount, transaction_date, and the previous amount.

Summary

What did they spend last time? Context changes everything.

Practice This Problem

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