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#0315
Total Revenue Per Customer
EasySQL15 min10 XP
Problem
Return customer_id and total_revenue, ordered by customer_id.
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, customer_id INTEGER, amount INTEGER)
Examples
Example 1
Inputcustomer 1 has two orders
Outputcustomer 1 -> 100, customer 2 -> 25
SUM(amount) is calculated inside each customer group.
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
Inputcustomer 1 has two orders
Expected[[1,100],[2,25]]
SUM(amount) is calculated inside each customer group.
Hidden Test Categories
Empty or missing matchesDuplicate rows or tiesNULL values where the pattern commonly breaks