Problem Description –
Write an SQL query to find the number of unique orders and the number of unique customers with invoices > $20 for each different month.
Return the result table sorted in any order.
The query result format is in the following example.


Problem Link – unique orders and customers
Difficulty Level – Easy
Solution –
SELECT
DATE_FORMAT(order_date, '%Y-%m') as month,
COUNT(DISTINCT order_id) as order_count,
COUNT(DISTINCT customer_id) as customer_count
FROM Orders
WHERE invoice > 20
GROUP BY 1