Issues with DISTINCT and GROUP BY causing unexpected duplicates in MySQL 8.0
I'm attempting to set up I'm working on a personal project and I tried several approaches but none seem to work....... Currently developing an inventory management application using MySQL 8.0 and I'm running into a perplexing issue with my SQL queries... I need to retrieve a list of unique products along with their total quantities sold, but despite using `DISTINCT`, I'm still seeing duplicate entries in the results. Here's the query I've written: ```sql SELECT DISTINCT p.product_id, p.product_name, SUM(o.quantity) AS total_quantity FROM products p JOIN orders o ON p.product_id = o.product_id GROUP BY p.product_id, p.product_name; ``` I expected this to return each product only once with the correct quantity, but instead, I'm getting multiple entries for some products. I've tried removing `DISTINCT`, but that just leads to a longer list with the same products repeated. To troubleshoot, I modified the query to: ```sql SELECT p.product_id, p.product_name, SUM(o.quantity) AS total_quantity FROM products p LEFT JOIN orders o ON p.product_id = o.product_id GROUP BY p.product_id, p.product_name; ``` This version gives me correct totals, yet the duplicates are still present when products have no associated orders. The output looks like this: | product_id | product_name | total_quantity | |------------|--------------|----------------| | 1 | Widget | 10 | | 1 | Widget | 10 | | 2 | Gadget | 5 | | 3 | Thingamajig | NULL | I’m also aware that MySQL allows for non-aggregated columns in the `GROUP BY` clause, which is why I included both `product_id` and `product_name`, but it’s not yielding the expected result. Could this behavior be related to how NULL values are handled in the `SUM` function? Looking for advice on how to properly structure this query to avoid duplicates while still getting the total quantities. Any insights or recommendations on this would be greatly appreciated! I'm working on a application that needs to handle this. Thanks in advance! For context: I'm using Sql on Windows. How would you solve this? This is part of a larger CLI tool I'm building. What am I doing wrong? My development environment is Ubuntu 20.04. For reference, this is a production web app. I'm open to any suggestions.