MySQL 5.7: implementing Group By and Aggregate Functions in Complex Queries
I'm experimenting with I'm stuck on something that should probably be simple..... I'm working on a personal project and I am working with an scenario with MySQL 5.7 when trying to use `GROUP BY` with multiple aggregate functions in a complex query. The query is quite straightforward, but I am getting unexpected results. Here’s the SQL I am using: ```sql SELECT a.category, COUNT(b.id) AS total_items, SUM(b.price) AS total_price FROM categories AS a JOIN items AS b ON a.id = b.category_id WHERE b.stock > 0 GROUP BY a.category; ``` The goal is to count the number of items in each category and sum their prices, but instead, I am getting duplicate counts for the same category. For instance, the result for category 'Electronics' shows 10 items instead of the expected 5. I have checked the data in both tables, and it seems correct. I also tried adding a `DISTINCT` clause: ```sql SELECT a.category, COUNT(DISTINCT b.id) AS total_items, SUM(b.price) AS total_price FROM categories AS a JOIN items AS b ON a.id = b.category_id WHERE b.stock > 0 GROUP BY a.category; ``` However, this did not solve the scenario, and the result remains the same. Additionally, I'm aware that MySQL allows some non-standard behaviors with `GROUP BY`, and I have checked the SQL mode using: ```sql SELECT @@sql_mode; ``` It returns `STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION`, so it should be compliant with standard SQL behaviors. The question continues even when I simplify the query. I would greatly appreciate any insights or suggestions on how to resolve this scenario or what I might be missing in the logic. For context: I'm using Sql on Linux. What's the best practice here? This is part of a larger service I'm building. Any pointers in the right direction? I'd be grateful for any help.