MySQL 8.0: Incorrect Row Count with GROUP BY and HAVING Clause in Subquery
I'm updating my dependencies and Quick question that's been bugging me - After trying multiple solutions online, I still can't figure this out..... I've looked through the documentation and I'm still confused about I'm working with an scenario with a query that uses a subquery along with GROUP BY and HAVING clauses in MySQL 8.0... The goal is to count the number of orders per customer, but I keep getting unexpected results for the row count. I've tried to simplify the query but still need to get the expected output. Here's a snippet of my SQL query: ```sql SELECT customer_id, COUNT(order_id) as total_orders FROM ( SELECT customer_id, order_id FROM orders WHERE order_date >= '2023-01-01' ) AS subquery GROUP BY customer_id HAVING total_orders > 5; ``` When I run this, I expect to see customers who have made more than 5 orders since the beginning of the year. However, the result set shows customers with only 3 orders listed, which contradicts the HAVING condition. I've also verified the data in the `orders` table and confirmed that there are customers with more than 5 orders within the specified date range. I've tried rewriting the query without the subquery: ```sql SELECT customer_id, COUNT(order_id) as total_orders FROM orders WHERE order_date >= '2023-01-01' GROUP BY customer_id HAVING total_orders > 5; ``` This gives me a correct count, but I need to use the subquery for additional filtering in a larger query context. I also checked for NULL values and confirmed that `order_id` is never NULL in the `orders` table. Is there something I'm missing about how the GROUP BY and HAVING clauses work with subqueries in MySQL? Any insights or suggestions on how to resolve this would be greatly appreciated! This is part of a larger service I'm building. How would you solve this? What's the best practice here? Is there a simpler solution I'm overlooking? I'm working in a Debian environment.