SQL Server query returning incorrect results with LEFT JOIN and GROUP BY
I'm working on a project and hit a roadblock. I'm prototyping a solution and I've been struggling with this for a few days now and could really use some help. I'm working with SQL Server 2019 and I've run into a frustrating issue where my query is not returning the expected results when I use a LEFT JOIN combined with GROUP BY. I'm trying to get a count of orders per customer, including customers who have not placed any orders. Here's the query I wrote: ```sql SELECT c.CustomerID, c.CustomerName, COUNT(o.OrderID) AS OrderCount FROM Customers c LEFT JOIN Orders o ON c.CustomerID = o.CustomerID GROUP BY c.CustomerID, c.CustomerName; ``` The intention is to list all customers along with the number of orders they have placed. However, the output shows multiple rows for customers with no orders, sometimes even resulting in a count of zero being presented incorrectly as multiple rows like this: ``` CustomerID | CustomerName | OrderCount ------------|---------------|------------ 1 | John Doe | 0 1 | John Doe | 0 2 | Jane Smith | 2 3 | Mike Johnson | 0 ``` I’ve double-checked that the data in the `Orders` table is accurate and that there are indeed customers with no orders. It's perplexing that the same customer appears multiple times with the same order count. I've also tried to simplify the query without the GROUP BY clause and that returns the correct unique rows, but I need the counts. Additionally, I ensured there are no duplicate entries in the `Customers` table. What could be causing this behavior? Am I missing something in the JOIN logic or the GROUP BY clause? Any suggestions would be appreciated! What am I doing wrong? Has anyone else encountered this?