SQL Server: Getting Incorrect Results with Recursive CTE for Hierarchical Data
I'm working on a personal project and I just started working with I'm having trouble with I'm working with SQL Server 2019 and trying to retrieve hierarchical data using a recursive Common Table Expression (CTE)....... The structure is a simple employee table with an `EmployeeID`, `ManagerID`, and `Name`. I want to get a list of all employees starting from a specific manager and their subordinates at all levels. However, my results are not what I expected; I keep getting repeated entries for some employees, and the recursion seems to be going deeper than it should. Here's the query I've been using: ```sql WITH RecursiveCTE AS ( SELECT EmployeeID, Name, ManagerID, 0 AS Level FROM Employees WHERE EmployeeID = @StartEmployeeID -- Starting point for recursion UNION ALL SELECT e.EmployeeID, e.Name, e.ManagerID, Level + 1 FROM Employees e INNER JOIN RecursiveCTE r ON e.ManagerID = r.EmployeeID ) SELECT * FROM RecursiveCTE; ``` When I run this with `@StartEmployeeID = 3`, I expect to get all employees under that manager, but I see duplicates in the output and some employees are listed multiple times. I suspect it might be due to how I'm joining in the recursive part, but I'm not sure how to fix it. I've tried adding a `DISTINCT` clause to the final select, but that doesn't resolve the issue, and it may hide some of the necessary data I need. I also checked for circular references in the data, but it appears to be a clean hierarchy. Any insights on why I'm getting these unexpected duplicates and how to ensure the recursion behaves correctly? Are there any best practices I should be following when working with recursive CTEs for hierarchical queries in SQL Server? Am I missing something obvious? What are your experiences with this? This issue appeared after updating to Sql stable. Cheers for any assistance! Has anyone dealt with something similar?