Question

1174. Immediate Food Delivery II

中文文档

Description

Table: Delivery

+-----------------------------+---------+
| Column Name         | Type  |
+-----------------------------+---------+
| delivery_id         | int   |
| customer_id         | int   |
| order_date          | date  |
| customer_pref_delivery_date | date  |
+-----------------------------+---------+
delivery_id is the column of unique values of this table.
The table holds information about food delivery to customers that make orders at some date and specify a preferred delivery date (on the same order date or after it).

 

If the customer's preferred delivery date is the same as the order date, then the order is called immediate; otherwise, it is called scheduled.

The first order of a customer is the order with the earliest order date that the customer made. It is guaranteed that a customer has precisely one first order.

Write a solution to find the percentage of immediate orders in the first orders of all customers, rounded to 2 decimal places.

The result format is in the following example.

 

Example 1:

Input: 
Delivery table:
+-------------+-------------+------------+-----------------------------+
| delivery_id | customer_id | order_date | customer_pref_delivery_date |
+-------------+-------------+------------+-----------------------------+
| 1       | 1       | 2019-08-01 | 2019-08-02          |
| 2       | 2       | 2019-08-02 | 2019-08-02          |
| 3       | 1       | 2019-08-11 | 2019-08-12          |
| 4       | 3       | 2019-08-24 | 2019-08-24          |
| 5       | 3       | 2019-08-21 | 2019-08-22          |
| 6       | 2       | 2019-08-11 | 2019-08-13          |
| 7       | 4       | 2019-08-09 | 2019-08-09          |
+-------------+-------------+------------+-----------------------------+
Output: 
+----------------------+
| immediate_percentage |
+----------------------+
| 50.00        |
+----------------------+
Explanation: 
The customer id 1 has a first order with delivery id 1 and it is scheduled.
The customer id 2 has a first order with delivery id 2 and it is immediate.
The customer id 3 has a first order with delivery id 5 and it is scheduled.
The customer id 4 has a first order with delivery id 7 and it is immediate.
Hence, half the customers have immediate first orders.

Solutions

Solution 1: Subquery

We can use a subquery to first find the first order of each user, and then calculate the proportion of instant orders.

# Write your MySQL query statement below
SELECT
  ROUND(AVG(order_date = customer_pref_delivery_date) * 100, 2) AS immediate_percentage
FROM Delivery
WHERE
  (customer_id, order_date) IN (
    SELECT customer_id, MIN(order_date)
    FROM Delivery
    GROUP BY 1
  );

Solution 2: Window Function

We can use the RANK() window function to rank the orders of each user in ascending order by order date, and then filter out the orders with a rank of $1$, which are the first orders of each user. After that, we can calculate the proportion of instant orders.

# Write your MySQL query statement below
WITH
  T AS (
    SELECT
      *,
      RANK() OVER (
        PARTITION BY customer_id
        ORDER BY order_date
      ) AS rk
    FROM Delivery
  )
SELECT
  ROUND(AVG(order_date = customer_pref_delivery_date) * 100, 2) AS immediate_percentage
FROM T
WHERE rk = 1;