How to make hierarchy path from bottom SQL Server - sql

Question

I'm trying to make reverse hierarchy path.
This is for path manager-subordinate
WITH CTE_Path AS
(
SELECT
P1.EmployeeID, P1.ManagerID,
CAST(FirstName + LastName AS NVARCHAR(MAX)) AS PathHierarchy,
1 AS level
FROM
EmployeesManagers AS P1
WHERE
ManagerID IS NULL
UNION ALL
SELECT
P2.EmployeeID, P2.ManagerID,
CONCAT(CAST(C.PathHierarchy AS NVARCHAR(MAX)), N' > ',
CAST(P2.FirstName+LastName AS NVARCHAR(MAX))), level + 1
FROM
EmployeesManagers AS P2
JOIN
CTE_Path AS C ON C.EmployeeID = P2.ManagerID
)
SELECT PathHierarchy
FROM CTE_Path
Data for this
CREATE TABLE dbo.EmployeesManagers
(
EmployeeID int NOT NULL PRIMARY KEY,
FirstName varchar(50) NOT NULL,
LastName varchar(50) NOT NULL,
ManagerID int NULL
)
GO
INSERT INTO EmployeesManagers VALUES (101, 'Ken', 'Sánchez', NULL)
INSERT INTO EmployeesManagers VALUES (102, 'Terri', 'Duffy', 101)
INSERT INTO EmployeesManagers VALUES (103, 'Roberto', 'Tamburello', 101)
INSERT INTO EmployeesManagers VALUES (104, 'Rob', 'Walters', 102)
INSERT INTO EmployeesManagers VALUES (105, 'Gail', 'Erickson', 102)
INSERT INTO EmployeesManagers VALUES (106, 'Jossef', 'Goldberg', 103)
INSERT INTO EmployeesManagers VALUES (107, 'Dylan', 'Miller', 103)
INSERT INTO EmployeesManagers VALUES (108, 'Diane', 'Margheim', 105)
INSERT INTO EmployeesManagers VALUES (109, 'Gigi', 'Matthew', 105)
INSERT INTO EmployeesManagers VALUES (110, 'Michael', 'Raheem', 106)
And I need subordinate-manager-manager1 - ...
What to change here? Anchor or recursive part?
Is it possible to create function where you can give argument EmployeeID and it will return path employee-manager-manager1-ceoOfCompany?

Answer 1

You can reverse the logic by starting where employees are not a manager and then tweak the join in the second part of the recursive subquery:
WITH CTE AS (
SELECT P1.EmployeeID, P1.ManagerID, CAST(FirstName+LastName AS NVARCHAR(MAX)) AS PathHierarchy, 1 as level
FROM EmployeesManagers AS P1
WHERE NOT EXISTS (SELECT 1 FROM EmployeesManagers em2 WHERE EM2.ManagerID = p1.EmployeeId)
UNION ALL
SELECT P2.EmployeeID, P2.ManagerID, CONCAT(CAST(C.PathHierarchy AS NVARCHAR(MAX)), N' > ', CAST(P2.FirstName+LastName AS NVARCHAR(MAX))), level+1
FROM CTE c JOIN
EmployeesManagers P2
ON P2.EmployeeID = C.ManagerID
)
SELECT PathHierarchy
FROM CTE;
Here is a db<>fiddle.