1174 Immediate Food Delivery II

Description

Table: Delivery

• delivery_id is the primary key (column with 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.

Problem Statement

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:

Output:

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.

Solution

The problem is asking to find the percentage of first orders which are immediate orders. In order to reach this solution, you first need to find the first orders for each customer. The next task is to check how many of those orders are immediate orders and divide this number with total number of first orders.

 1WITH first_orders AS (
 2    SELECT customer_id, MIN(order_date) AS order_date
 3        FROM Delivery
 4        GROUP BY customer_id
 5) SELECT ROUND(
 6        SUM(CASE WHEN order_date = customer_pref_delivery_date THEN 1 ELSE 0 END) /
 7        COUNT(1) * 100, 2
 8    ) AS immediate_percentage
 9    FROM Delivery
10    WHERE (customer_id, order_date) IN (
11        SELECT * FROM first_orders
12    );

Alternatively, you can use AVG() function to find the average.

1SELECT ROUND(AVG(order_date = customer_pref_delivery_date) * 100, 2)  AS immediate_percentage
2    FROM Delivery
3    WHERE (customer_id, order_date) IN (
4        SELECT customer_id, MIN(order_date) AS order_date
5        FROM Delivery
6        GROUP BY customer_id
7    );