LeetCode: Customer Placing the Largest Number of Orders

LeetCode: Customer Placing the Largest Number of Orders

Query the customer_number from the orders table for the customer who has placed the largest number of orders.

It is guaranteed that exactly one customer will have placed more orders than any other customer.

The orders table is defined as follows:

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| Column            | Type      |
|-------------------|-----------|
| order_number (PK) | int |
| customer_number | int |
| order_date | date |
| required_date | date |
| shipped_date | date |
| status | char(15) |
| comment | char(200) |

Sample Input

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| order_number | customer_number | order_date | required_date | shipped_date | status | comment |
|--------------|-----------------|------------|---------------|--------------|--------|---------|
| 1 | 1 | 2017-04-09 | 2017-04-13 | 2017-04-12 | Closed | |
| 2 | 2 | 2017-04-15 | 2017-04-20 | 2017-04-18 | Closed | |
| 3 | 3 | 2017-04-16 | 2017-04-25 | 2017-04-20 | Closed | |
| 4 | 3 | 2017-04-18 | 2017-04-28 | 2017-04-25 | Closed | |

Sample Output

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

Explanation

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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'.

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# Write your MySQL query statement below
select customer_number from (select customer_number, count(*) as count from orders group by customer_number order by count desc) t limit 1