advanced patterns when using CTE with Recursive Query in SQL Server 2019
Quick question that's been bugging me - I'm writing unit tests and I'm working with an scenario with a Common Table Expression (CTE) that uses recursion in SQL Server 2019... My goal is to generate a hierarchy of employees, where each employee can have multiple direct reports. However, the query returns inconsistent results when there are employees with no direct reports. Here's the CTE I am using: ```sql WITH EmployeeHierarchy AS ( SELECT EmployeeID, ManagerID, EmployeeName, 0 AS Level FROM Employees WHERE ManagerID IS NULL UNION ALL SELECT e.EmployeeID, e.ManagerID, e.EmployeeName, eh.Level + 1 FROM Employees e INNER JOIN EmployeeHierarchy eh ON e.ManagerID = eh.EmployeeID ) SELECT * FROM EmployeeHierarchy; ``` I expect to see all employees listed, even those without direct reports. However, what I get is a truncated list where some employees seem to vanish from the results if they don't have any children. When I run the same query on a smaller dataset, it works fine, but with our production data, it fails to return the expected full hierarchy. I've tried adjusting the base case of the CTE and using different joins but to no avail. I also checked for circular references, and the data integrity seems fine. Additionally, when inspecting the execution plan, I notice that there are some warnings about missing statistics, but Iām not sure how to address that without impacting performance. Can someone guide to understand why this might be happening and how to ensure all employees show up in the results? What's the best practice here? What are your experiences with this? Is there a simpler solution I'm overlooking? Is there a better approach?