MEDIUM

Author: evanmathew

1174. Immediate Food Delivery II.sql

@@ -1,2 +1,62 @@
+-- Problem:
+
+/*
+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.
+*/
+
+-------------------------------------------------------------------------------
+
+-- Solution:
+
 SELECT ROUND(SUM(IF(order_date=customer_pref_delivery_date,1,0))/ COUNT(*) *100,2) AS immediate_percentage FROM Delivery
 WHERE (customer_id,order_date) IN (SELECT customer_id, MIN(order_date) FROM Delivery GROUP BY customer_id)