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3293. Calculate Product Final Price πŸ”’

Description

Table: Products

+------------+---------+ 
| Column Name| Type    | 
+------------+---------+ 
| product_id | int     | 
| category   | varchar |
| price      | decimal |
+------------+---------+
product_id is the unique key for this table.
Each row includes the product's ID, its category, and its price.

Table: Discounts

+------------+---------+ 
| Column Name| Type    | 
+------------+---------+ 
| category   | varchar |
| discount   | int     |
+------------+---------+
category is the primary key for this table.
Each row contains a product category and the percentage discount applied to that category (values range from 0 to 100).

Write a solution to find the final price of each product after applying the category discount. If a product's category has no associated discount, its price remains unchanged.

Return the result table ordered by product_id in ascending order.

The result format is in the following example.

 

Example:

Input:

Products table:

+------------+-------------+-------+
| product_id | category    | price |
+------------+-------------+-------+
| 1          | Electronics | 1000  |
| 2          | Clothing    | 50    |
| 3          | Electronics | 1200  | 
| 4          | Home        | 500   |
+------------+-------------+-------+

Discounts table:

+------------+----------+
| category   | discount |
+------------+----------+
| Electronics| 10       |
| Clothing   | 20       |
+------------+----------+

Output:

+------------+------------+-------------+
| product_id | final_price| category    |
+------------+------------+-------------+
| 1          | 900        | Electronics |
| 2          | 40         | Clothing    |
| 3          | 1080       | Electronics |
| 4          | 500        | Home        |
+------------+------------+-------------+

Explanation:

  • For product 1, it belongs to the Electronics category which has a 10% discount, so the final price is 1000 - (10% of 1000) = 900.
  • For product 2, it belongs to the Clothing category which has a 20% discount, so the final price is 50 - (20% of 50) = 40.
  • For product 3, it belongs to the Electronics category and receives a 10% discount, so the final price is 1200 - (10% of 1200) = 1080.
  • For product 4, no discount is available for the Home category, so the final price remains 500.
Result table is ordered by product_id in ascending order.

Solutions

Solution 1: Left Join

We can perform a left join between the Products table and the Discounts table on the category column, then calculate the final price. If a product's category does not have an associated discount, its price remains unchanged.

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# Write your MySQL query statement below
SELECT
    product_id,
    price * (100 - IFNULL(discount, 0)) / 100 final_price,
    category
FROM
    Products
    LEFT JOIN Discounts USING (category)
ORDER BY 1;

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import pandas as pd


def calculate_final_prices(
    products: pd.DataFrame, discounts: pd.DataFrame
) -> pd.DataFrame:
    # Perform a left join on the 'category' column
    merged_df = pd.merge(products, discounts, on="category", how="left")

    # Calculate the final price
    merged_df["final_price"] = (
        merged_df["price"] * (100 - merged_df["discount"].fillna(0)) / 100
    )

    # Select the necessary columns and sort by 'product_id'
    result_df = merged_df[["product_id", "final_price", "category"]].sort_values(
        "product_id"
    )

    return result_df

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