SQL Employee Org Hierarchy - sql-server

Question

I have an employee table.
Employee
Supervisor
YearMonth
a
b
202201
b
c
202201
c
null
202201
e
b
202202
b
d
202202
And I want to create an org hierarchy that is at a column level in SQL expected output =
Employee
Supervisor
YearMonth
Org1
Org2
a
b
202201
b
c
b
c
202201
c
null
c
null
202201
null
null
e
b
202202
b
d
b
d
202202
d
null
I have been able to achieve this in python, but want the same output in SQL.

Answer 1

I've tried to get what you want but maybe you have provided dud data!?
as Employee b is listed twice so he has supervisor c and d, hence why the example below differ from what you want.
I've provided 3 types or approaches, run them all and see what you think, I think the third one is closest to what you want
IF EXISTS (SELECT * FROM tempdb.dbo.sysobjects O WHERE O.xtype in ('U') AND O.id = object_id(N'tempdb..#Employee'))
BEGIN
PRINT 'Removing temp table #Employee'
DROP TABLE #Employee;
END
CREATE TABLE #Employee (
EmployeeId VARCHAR(1),
SupervisorId VARCHAR(1),
YearMonth VARCHAR(6)
)
INSERT INTO #Employee (EmployeeId, SupervisorId, YearMonth)
VALUES('a', 'b', '202201'),
('b', 'c', '202201'),
('c', NULL, '202201'),
('e', 'b', '202202'),
('b', 'd', '202202')
-- SELECT * FROM #Employee
/*
Approach 1: Use a CTE to recursively get the hierarchy
*/
;WITH MyTable AS
(
SELECT EmployeeId, SupervisorId, 1 AS [Level]
FROM #Employee
WHERE EmployeeId = 'a' -- Remove this to get everyone and the levels of hierarchy
UNION ALL
SELECT e.EmployeeId, e.SupervisorId, T.[Level] + 1
FROM #Employee AS E
INNER JOIN MyTable AS T ON T.SupervisorId = E.EmployeeId
)
SELECT * FROM MyTable
ORDER BY [Level] ASC
/*
Approach 2:
What you are asking is just display the manager for employee and supervisor
But this has more data as supervisor b has more than one supervisor
*/
SELECT
E.EmployeeId AS Employee,
E.SupervisorId AS Supervisor,
E.YearMonth,
E.SupervisorId AS Org1,
E2.SupervisorId AS Org2
FROM #Employee AS E
LEFT JOIN #Employee AS E2 ON E2.EmployeeId = E.SupervisorId
GO
/*
Approach 3:
Using a outer apply will just get the data for each row
*/
SELECT
E.EmployeeId AS Employee,
E.SupervisorId AS Supervisor,
E.YearMonth,
E.SupervisorId AS Org1,
T.SupervisorId AS Org2
FROM #Employee AS E
OUTER APPLY (
SELECT TOP 1 *
FROM #Employee AS E2
WHERE E2.EmployeeId = E.SupervisorId
) AS T
Output to show, note the first one I just focus on Employee a but you can remove that to get everyone's hierarchy and display the level they are in.