Solution Explanation for Calculating the Average Selling Price of Products
Steps to the Solution\nHere is a step-by-step approach to solve the problem:\n\n- Join the Tables: \n    - We will perform a LEFT JOIN between the Prices and Un
# Steps to the Solution\nHere is a step-by-step approach to solve the problem:\n\n- **Join the Tables**: \n    - We will perform a `LEFT JOIN` between the `Prices` and `UnitsSold` tables to combine pricing and sales information.\n    - The `ON` clause establishes the condition for the join: `ON p.product_id = u.product_id`, linking rows from both tables where the `product_id` matches.\n    - To ensure that each sale reflects the correct price according to the date of the transaction, we will include a condition using `BETWEEN` within the `ON` clause: `AND purchase_date BETWEEN start_date AND end_date`. This ensures that only the prices valid at the time of each sale are considered, accurately aligning each sale with its corresponding price.\n\n- **Calculate the Weighted Average Price**:\n\n    - For each product, we will multiply the price by the number of units sold. This will give us the total revenue for that product.\n    - Next, we will sum these total revenues and divide by the total number of units sold to obtain the weighted average price.\n    - We will use the `COALESCE` function to handle cases where there are no sales: if no units have been sold, we will assume the average price is `0`.\n\n- **Group the Results**: \n    - Finally, we will group the results by `product_id` to ensure we have an average for each product.\n\n# Code\n```mysql []\nSELECT p.product_id, COALESCE(ROUND(SUM(p.price * u.units) / SUM(u.units), 2), 0) AS average_price\nFROM Prices p\nLEFT JOIN UnitsSold u \n    ON p.product_id = u.product_id\n    AND purchase_date BETWEEN start_date AND end_date\nGROUP BY p.product_id;\n```\n```MSSQL []\nSELECT p.product_id, COALESCE(ROUND(SUM(p.price * u.units * 1.0) / SUM(u.units), 2), 0) AS average_price\nFROM Prices p\nLEFT JOIN UnitsSold u \n    ON p.product_id = u.product_id\n    AND purchase_date BETWEEN start_date AND end_date\nGROUP BY p.product_id;\n```\n```Oracle []\nSELECT p.product_id, COALESCE(ROUND(SUM(p.price * u.units) / SUM(u.units), 2), 0) AS average_price\nFROM Prices p\nLEFT JOIN UnitsSold u \n    ON p.product_id = u.product_id\n    AND purchase_date BETWEEN start_date AND end_date\nGROUP BY p.product_id;\n```\n```PostgreSQL []\nSELECT p.product_id, COALESCE(ROUND(SUM(p.price * u.units * 1.0) / SUM(u.units), 2), 0) AS average_price\nFROM Prices p\nLEFT JOIN UnitsSold u \n    ON p.product_id = u.product_id\n    AND purchase_date BETWEEN start_date AND end_date\nGROUP BY p.product_id;\n```
['Database', 'MySQL', 'Oracle', 'MS SQL Server', 'PostgreSQL']