SQL Server: Why does my CTE return duplicate rows despite DISTINCT clause?
Can someone help me understand I'm trying to configure I'm performance testing and I'm wondering if anyone has experience with I'm working on a personal project and I've looked through the documentation and I'm still confused about I've searched everywhere and can't find a clear answer... I'm working with SQL Server 2019 and working with an scenario where my Common Table Expression (CTE) is returning duplicate rows, even though I've applied a DISTINCT clause in my final SELECT statement. The goal of my query is to fetch unique customer orders along with their total amounts, grouped by customer ID. Here’s the CTE I’m using: ```sql WITH OrderCTE AS ( SELECT CustomerID, OrderID, SUM(OrderAmount) AS TotalAmount FROM Orders GROUP BY CustomerID, OrderID ) SELECT DISTINCT CustomerID, TotalAmount FROM OrderCTE ORDER BY CustomerID; ``` Despite using DISTINCT, I still see duplicate entries for `CustomerID` in my result set. I've checked the data in the `Orders` table, and there are indeed multiple `OrderID`s per `CustomerID`, which is expected, but I thought the SUM function along with GROUP BY would handle that. I've also tried removing the `OrderID` from the `GROUP BY` clause and just grouping by `CustomerID`, but that only results in a single total amount per customer, which isn't what I need. The behavior I’m receiving in the output is quite misleading as it doesn’t indicate any scenario with the data retrieval process itself. Is there something specific about how CTEs work or how the DISTINCT clause interacts with grouped data that I'm missing? Any suggestions on how to resolve this would be greatly appreciated! My development environment is macOS. Thanks in advance! My development environment is Windows. Is there a better approach? Any ideas what could be causing this? I'm on Ubuntu 22.04 using the latest version of Sql. Could someone point me to the right documentation? I'm on Windows 11 using the latest version of Sql. What am I doing wrong? The stack includes Sql and several other technologies. Is there a better approach?