Yesterday's Weather

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

Domain

SQL

Difficulty

hard

Seniority

L4

Problem

A FinOps team benchmarks its cost models against the simplest possible forecast: whatever a month actually cost becomes next month's prediction. Total each month's real cloud spend, keeping only positive charges so that credits (posted as a negative `amount`) and unpriced items (a null `amount`) never distort the figure, and treat the prior month's total as the current month's forecast. Report each month's year-month, its actual cost, the forecast, and the absolute percent error of the forecast measured against that month's actual cost.

Summary

The forecast was off. By how much?

Practice This Problem

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