SQL Server: advanced patterns with CTE and Aggregation in a Recursive Query
I'm writing unit tests and I'm dealing with I'm prototyping a solution and This might be a silly question, but I'm working with unexpected behavior when using a Common Table Expression (CTE) for a recursive query in SQL Server 2019. I want to aggregate data from a hierarchical table, but the results aren't what I anticipated. My table structure looks like this: ```sql CREATE TABLE Employees ( EmployeeID INT PRIMARY KEY, ManagerID INT, Name NVARCHAR(100), Salary DECIMAL(10, 2) ); ``` I have the following recursive CTE to calculate the total salary of all employees under a specific manager: ```sql WITH EmployeeHierarchy AS ( SELECT EmployeeID, ManagerID, Name, Salary FROM Employees WHERE ManagerID IS NULL -- Starting point for recursion UNION ALL SELECT e.EmployeeID, e.ManagerID, e.Name, e.Salary FROM Employees e INNER JOIN EmployeeHierarchy eh ON e.ManagerID = eh.EmployeeID ) SELECT ManagerID, SUM(Salary) AS TotalSalary FROM EmployeeHierarchy GROUP BY ManagerID; ``` However, the output is returning NULL for `TotalSalary` where I expect a numerical value. I tried adding a `WHERE` clause to filter out NULL salaries but that didn't resolve the scenario. I've also attempted removing the `GROUP BY ManagerID` to see if it changes anything, but the same scenario continues. The recursive CTE seems to be working as expected since I can see all employees listed correctly when I run the CTE alone. Is there something I'm missing regarding how the aggregation works with recursive CTEs? Any insights or suggestions would be greatly appreciated. Thanks! Any ideas what could be causing this? The stack includes Sql and several other technologies. Am I missing something obvious? The stack includes Sql and several other technologies. What am I doing wrong? What are your experiences with this?