MySQL GROUP BY with CASE statement not aggregating correctly when using multiple columns
I'm trying to implement I need help solving I'm attempting to set up I'm currently working on a MySQL query to summarize sales data by month and product category, but I'm encountering issues with the aggregation not providing the expected results. The query looks something like this: ```sql SELECT DATE_FORMAT(order_date, '%Y-%m') AS order_month, product_category, SUM(CASE WHEN status = 'completed' THEN amount ELSE 0 END) AS total_sales FROM orders GROUP BY order_month, product_category ORDER BY order_month, product_category; ``` In this query, I'm trying to get the total sales for each product category per month. However, when I run it, I get results that seem to mix up the data. For instance, the `total_sales` for certain months appears as if it aggregates from an incorrect set of records. I even tried using `DISTINCT` in the `SUM`, but that didn't resolve the discrepancies. I also verified that the `status` values are being pulled correctly and that there aren't any unexpected `NULL` values in the `amount` column that could be affecting the aggregation. The database version is MySQL 8.0.23. Here's a snippet of the output I'm seeing: | order_month | product_category | total_sales | |-------------|------------------|-------------| | 2023-01 | Electronics | 300 | | 2023-01 | Apparel | 150 | | 2023-02 | Electronics | 450 | | 2023-02 | Electronics | 200 | Notice how there's an apparent duplication for `Electronics` in February. I've also experimented with removing the `product_category` from the `GROUP BY`, but that just leads to inflated sales figures. Any insights on how to correct this and ensure the aggregation is accurate would be greatly appreciated! What's the best practice here? I'm working on a service that needs to handle this. Hoping someone can shed some light on this. I'm using Sql stable in this project. Hoping someone can shed some light on this.