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#0385
Cancellation Rate by Category
MediumSQL24 min20 XP
Problem
Return category and cancel_rate as cancelled orders divided by total orders.
Why This Matters
SQL interviews usually test whether you can turn a business question into the right rows, grouping level, join type, and edge-case behavior.
Schema
orders(order_id INTEGER, category TEXT, status TEXT)
Examples
Example 1
InputA has 1 cancelled out of 2
OutputA 0.5, B 0
The numerator counts cancelled rows inside each category.
Constraints
- Return only the requested columns.
- Use deterministic ORDER BY when multiple rows are returned.
- Assume SQLite-compatible SQL unless the prompt states otherwise.
CodeSQL
Visible browser tests run here when available.
Testcases1 visible / 3 hidden categories
Core SQL case
InputA has 1 cancelled out of 2
Expected[["A",0.5],["B",0]]
The numerator counts cancelled rows inside each category.
Hidden Test Categories
Empty or missing matchesDuplicate rows or tiesNULL values where the pattern commonly breaks