MySQL query using multiple joins and CASE statement returns unexpected NULL values in result set
I'm prototyping a solution and Hey everyone, I'm running into an issue that's driving me crazy. This might be a silly question, but I'm working on a MySQL 8.0.25 project where I need to generate a report that combines data from three tables: `orders`, `customers`, and `products`. The goal is to display the customer name, product name, and total order value, but I'm getting unexpected NULL values in the results for some customers even though they have orders. Here's the query I've constructed: ```sql SELECT c.customer_name, p.product_name, SUM(o.order_value) AS total_order_value FROM customers c LEFT JOIN orders o ON c.customer_id = o.customer_id LEFT JOIN products p ON o.product_id = p.product_id GROUP BY c.customer_id, p.product_id; ``` This should return a list of all customers with their corresponding product names and total order values. However, I noticed that for some customers who have placed orders, the `total_order_value` comes back as NULL, and I want to figure out why. It's puzzling because I have verified that the customers do exist in the `orders` table and that their `order_value` entries are not NULL. I've tried modifying the query by switching to INNER JOINs, but that resulted in excluding customers without orders entirely, which is not what I want. I also played around with the GROUP BY clause, but it didn't help. Can someone explain why I'm seeing NULL values in the `total_order_value` field, and how I can adjust my query to ensure it returns the correct totals while still including customers without orders? I'm working on a REST API that needs to handle this. What's the best practice here?