#586 Customer Placing the Largest Number of Orders

https://leetcode.com/problems/customer-placing-the-largest-number-of-orders/

MS SQL Server

SELECT TOP 1 customer_number
FROM Orders
GROUP BY customer_number
ORDER BY COUNT(*) DESC;

SELECT customer_number
FROM (
    SELECT customer_number, row_number() 
    OVER (ORDER BY COUNT(DISTINCT order_number) DESC) rn
    FROM Orders
    GROUP BY customer_number) a
WHERE rn = 1