👀 Views: 294 💬 Answers: 1 📅 Created: 2025-06-10

MySQL JOIN GROUP BY SQL

I've tried everything I can think of but I've been banging my head against this for hours. I am working with an scenario with a query that is supposed to return the total sales for each product, but the sum seems to be inflated due to missing join conditions. I have two tables: `products` and `sales`. The `products` table contains product IDs and names, while the `sales` table has product IDs and the amount sold. Here’s what my current query looks like: ```sql SELECT p.product_id, p.product_name, SUM(s.amount) AS total_sales FROM products p LEFT JOIN sales s ON p.product_id = s.product_id GROUP BY p.product_id, p.product_name; ``` When I run this query, I get a total sales amount that seems way higher than what I expect, especially for products with no sales. I suspect that the scenario arises because I’m using a `LEFT JOIN`, which should include products without sales, but it seems to be causing duplicates when a product has multiple sales entries. I’ve tried adding a `DISTINCT` in the `SUM()` function like this: ```sql SELECT p.product_id, p.product_name, SUM(DISTINCT s.amount) AS total_sales FROM products p LEFT JOIN sales s ON p.product_id = s.product_id GROUP BY p.product_id, p.product_name; ``` However, this doesn’t solve the question and still results in inflated totals. I also considered whether I should filter out `NULL` amounts, but I don’t want to exclude products without sales. I am using MySQL version 8.0 and have checked that there are no unexpected duplicate entries in the `sales` table. Could someone guide to understand why the total sales are incorrect and suggest a proper way to achieve the desired result? Any help would be greatly appreciated! I'm using Sql LTS in this project.