LeetCode 코딩 테스트 - Immediate Food Delivery II(LV.Medium)

 

 

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.

 

# 쿼리를 작성하는 목표, 확인할 지표 : 첫주문 중에서 immediate(첫주문이=preffer_day)의 비율 / order_date, customer_pref_delivery_date 
# 쿼리 계산 방법 : 1. group by min을 사용해서 첫 주문과 첫 주문 했을 때의 pref_day 가져오기 -> 2. sum(pref_date와 같은 경우는 1 아니면 0) 으로 immediate가 몇 개인지 구하기 -> 3. immediate / first_order 로 비율 구하기 
# 데이터의 기간 : x
# 사용할 테이블 : delivery
# JOIN KEY : x
# 데이터 특징 : x
WITH base AS (
    SELECT 
        customer_id,
        # 1
        MIN(order_date) AS first_order,
        MIN(customer_pref_delivery_date) AS preff_date
    FROM delivery
    GROUP BY
        customer_id
)
SELECT
    # 3
    DISTINCT
        ROUND((immediate_cnt / total_cnt) * 100.0, 2) AS immediate_percentage
FROM (
SELECT
    COUNT(*) OVER() AS total_cnt,
    # 2
    SUM(CASE WHEN first_order = preff_date THEN 1 ELSE 0 END) OVER() AS immediate_cnt,
    CASE WHEN first_order = preff_date THEN 1 ELSE 0 
    END AS t_or_f
FROM base
) AS a