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1174. Immediate Food Delivery II
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.
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.
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# 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 );