LeetCode in Kotlin
1164. Product Price at a Given Date
Medium
SQL Schema
Table: Products
+---------------+---------+
| Column Name | Type |
+---------------+---------+
| product_id | int |
| new_price | int |
| change_date | date |
+---------------+---------+
(product_id, change_date) is the primary key of this table.
Each row of this table indicates that the price of some product was changed to a new price at some date.
Write an SQL query to find the prices of all products on 2019-08-16. Assume the price of all products before any change is 10.
Return the result table in any order.
The query result format is in the following example.
Example 1:
Input: Products table:
+------------+-----------+-------------+
| product_id | new_price | change_date |
+------------+-----------+-------------+
| 1 | 20 | 2019-08-14 |
| 2 | 50 | 2019-08-14 |
| 1 | 30 | 2019-08-15 |
| 1 | 35 | 2019-08-16 |
| 2 | 65 | 2019-08-17 |
| 3 | 20 | 2019-08-18 |
+------------+-----------+-------------+
Output:
+------------+-------+
| product_id | price |
+------------+-------+
| 2 | 50 |
| 1 | 35 |
| 3 | 10 |
+------------+-------+
Solution
# Write your MySQL query statement below
WITH before_change_date AS (
SELECT DISTINCT
product_id,
new_price as price,
RANK() Over(Partition By product_id Order by change_date DESC) as rnk
FROM Products
WHERE change_date <= '2019-08-16'
)
SELECT
product_id,
price
FROM before_change_date
WHERE rnk = 1
UNION
SELECT
DISTINCT product_id,
10 as price
FROM Products
WHERE product_id not in (
SELECT product_id
FROM Products
WHERE change_date <= '2019-08-16'
)