SQL Server 2019 - Deadlock implementing Recursive Common Table Expressions in Hierarchical Queries
I'm working with persistent deadlock issues when running a recursive Common Table Expression (CTE) in SQL Server 2019 to fetch hierarchical data from an employee table. The CTE is designed to retrieve all subordinates for a given employee, but under heavy load, it seems to cause deadlocks that result in a timeout behavior: `Transaction (Process ID 123) was deadlocked on lock resources with another process and has been chosen as the deadlock victim`. I've tried adding hints like `WITH (NOLOCK)` and using the `OPTION (MAXRECURSION 100)` directive, but the deadlocks still occur intermittently. Here’s the CTE code I'm using: ```sql WITH EmployeeHierarchy AS ( SELECT EmployeeID, ManagerID, Name, 0 AS Level FROM Employees WHERE EmployeeID = @EmployeeID UNION ALL SELECT e.EmployeeID, e.ManagerID, e.Name, Level + 1 FROM Employees e INNER JOIN EmployeeHierarchy eh ON eh.EmployeeID = e.ManagerID ) SELECT * FROM EmployeeHierarchy; ``` I've also tried using a temporary table to store intermediate results, but that didn't alleviate the deadlocks either. Additionally, I've gone through the execution plan and it shows that the CTE is getting evaluated multiple times. Is there a more efficient way to structure this query or strategies I could apply to prevent deadlocks? Any advice would be greatly appreciated! What's the correct way to implement this?