employee-manager relationship hierarchy using SQL Query

 

As you can see, I had to put a hardcoded value for EMPLEVEL field in the Recursive section of the query above. This was because I did not join the Recursive section of the query with our recursive CTE. Now, in order to make the entire hierarchical query work with actual hierarchical level of records assigned, we need to complete the INNER JOIN as in the below query. Notice the difference in value of EMPLEVEL field. This is the complete hierarchical query in CTE format. Please note that ORDER BY is optional here.

WITH OURCTE (EMPNO, ENAME, MGR, EMPLEVEL)
AS (SELECT EMPNO, ENAME, MGR, 1 EMPLEVEL ---Initial Subquery
FROM Emp
WHERE MGR IS NULL
UNION ALL
SELECT E.EMPNO, E.ENAME, E.MGR, CTE.EMPLEVEL + 1 ---Recursive Subquery
FROM EMP E
INNER JOIN OURCTE CTE ON E.MGR = CTE.EMPNO –Inner Join
WHERE E.MGR IS NOT NULL)
SELECT *
FROM OURCTE
ORDER BY EMPLEVEL;

If you need to display the manager name next to the manager ID, refer to the following query:

SELECT CTE.EMPNO, CTE.ENAME, CTE.MGR, E.ENAME “MGR NAME”, CTE.EMPLEVEL
FROM (
WITH OURCTE (EMPNO, ENAME, MGR, EMPLEVEL)
AS (SELECT EMPNO, ENAME, MGR, 1 EMPLEVEL –Initial Subquery
FROM Emp
WHERE MGR IS NULL
UNION ALL
SELECT E.EMPNO, E.ENAME, E.MGR, CTE.EMPLEVEL + 1 –Recursive Subquery
FROM EMP E
INNER JOIN OURCTE CTE ON E.MGR = CTE.EMPNO
WHERE E.MGR IS NOT NULL)
SELECT *
FROM OURCTE
ORDER BY EMPLEVEL) CTE
LEFT OUTER JOIN EMP E ON CTE.MGR = E.EMPNO
ORDER BY CTE.EMPLEVEL,E.ENAME;