Unexpected Behavior with T-SQL Recursive CTE Returning Extra Rows in SQL Server 2019
I just started working with I'm working through a tutorial and I'm prototyping a solution and I'm working with a recursive Common Table Expression (CTE) in SQL Server 2019 to traverse a hierarchical data structure, but I'm encountering an unexpected issue where the CTE seems to be returning extra rows that I don't expect. I've defined my CTE to fetch parent-child relationships from an `Employees` table where each employee can have multiple subordinates. The hierarchy is structured as follows: ```sql CREATE TABLE Employees ( EmployeeID INT PRIMARY KEY, Name NVARCHAR(100), ManagerID INT, FOREIGN KEY (ManagerID) REFERENCES Employees(EmployeeID) ); ``` My recursive CTE is defined like this: ```sql WITH EmployeeHierarchy AS ( SELECT EmployeeID, Name, ManagerID, 0 AS Level FROM Employees WHERE ManagerID IS NULL UNION ALL SELECT e.EmployeeID, e.Name, e.ManagerID, eh.Level + 1 FROM Employees e INNER JOIN EmployeeHierarchy eh ON e.ManagerID = eh.EmployeeID ) SELECT * FROM EmployeeHierarchy; ``` When I run this query, it returns more rows than I expect, particularly some entries that appear to be duplicates or unrelated to the root nodes I targeted. I noticed that sometimes the `Level` column increments unexpectedly, leading me to believe that the recursive join might be incorrectly referencing rows. I've tried adding additional filtering conditions in both the anchor and recursive parts of the CTE, but the issue persists. Here's an example of the additional filter I attempted: ```sql SELECT * FROM EmployeeHierarchy WHERE Level <= 2; ``` Despite this, I'm still seeing rows that should not be part of the results. I've also checked for circular references in my data but didn’t find any. Is there a solution to ensure that the CTE only returns the intended hierarchical structure without extraneous rows, or could there be a specific behavior in SQL Server 2019 that I'm overlooking? Any insights would be greatly appreciated! I'm working in a Windows 11 environment. I'm working on a web app that needs to handle this. I'd be grateful for any help. My team is using Sql for this service.