[SQL] 리트코드 586. Customer Placing the Largest Number of Orders

문제

Table: Orders

+-----------------+----------+
| Column Name     | Type     |
+-----------------+----------+
| order_number    | int      |
| customer_number | int      |
+-----------------+----------+

order_number is the primary key (column with unique values) for this table.
This table contains information about the order ID and the customer ID.
 
Write a solution to find the customer_number for the customer who has placed the largest number of orders.
The test cases are generated so that exactly one customer will have placed more orders than any other customer.

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

Customer Placing the Largest Number of Orders - LeetCode

예시

Input: 
Orders table:

+--------------+-----------------+
| order_number | customer_number |
+--------------+-----------------+
| 1            | 1               |
| 2            | 2               |
| 3            | 3               |
| 4            | 3               |
+--------------+-----------------+

Output: 

+-----------------+
| customer_number |
+-----------------+
| 3               |
+-----------------+

Explanation: 
The customer with number 3 has two orders, which is greater than either customer 1 or 2 because each of them only has one order. 
So the result is customer_number 3.

문제 풀이

SELECT customer_number
FROM orders
GROUP BY customer_number
ORDER BY COUNT(order_number) DESC
LIMIT 1;

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SQL을 독학하시는 분들에게 도움이 되길 바라며,

혹 더 좋은 방법이 있거나 오류가 있다면 편하게 말씀 부탁드립니다.