DashCoreHub
Mission M35 · AI · 20 min
Ask AI for SQL — verify the count
Request from your manager
The loyalty manager asked an AI assistant: "How many loyalty members bought something in 2025?" It answered with SELECT COUNT(*) FROM orders o JOIN customers c ON c.customer_id = o.customer_id WHERE c.loyalty_member = 1 AND o.order_date >= '2025-01-01' — and got 3,344. That seems like a lot for the program. Check it.
Data
Download the practice file(s):
Steps
- Run the AI query exactly as written and confirm it returns 3,344.
- Ask yourself what one row represents after the join: one order, not one customer.
- Check the total: SELECT COUNT(*) FROM customers WHERE loyalty_member = 1. Can 3,344 people come from that?
- Fix the query with COUNT(DISTINCT o.customer_id) and an explicit upper date bound.
- Tell the AI what was wrong and ask it to explain the difference — a good way to learn and to test it.
Check your answer
How many distinct loyalty members placed at least one order in 2025?
Show solution
COUNT(*) counted orders (3,344). Counting distinct customers gives 800 loyalty members who bought in 2025.
SELECT COUNT(DISTINCT o.customer_id) AS loyalty_buyers_2025
FROM orders o
JOIN customers c ON c.customer_id = o.customer_id
WHERE c.loyalty_member = 1
AND o.order_date BETWEEN '2025-01-01' AND '2025-12-31';Answer: 800 rows