Yesterday's Weather
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
- L4
Interview Prompt
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?
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