Cost Efficiency Variance
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
- L5
Interview Prompt
For each billing entry, compute the cost-per-service ratio (amount divided by the number of services in that region). Then find the monthly average of these ratios. For each year-month, show the average ratio, the monthly average, and the average absolute difference between individual ratios and that month's average.
Summary
Cost efficiency varies. 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