Recursive CTE-Find all Employees Below Manager

问题

I created a sample fiddle for this SQLFIDDLE

CREATE TABLE [dbo].[Users](
    [userId] [int] ,
    [userName] [varchar](50) ,
    [managerId] [int] ,
   )

INSERT INTO dbo.Users
    ([userId], [userName], [managerId])
VALUES
(1,'Darry',NULL),
(2,'Cono',1),
(3,'Abros',2),
(4,'Natesh',1),
(5,'Ani',3),
(6,'Raju',5),
(7,'Pinky',5),
(8,'Miya',4)

My requirement is like displaying all employees hierarchy below that particular manager

Here is what i tried

WITH UserCTE AS (
  SELECT userId, userName, managerId, 0 AS EmpLevel
  FROM Users where managerId IS NULL

  UNION ALL

  SELECT usr.userId, usr.userName, usr.managerId, mgr.[EmpLevel]+1
  FROM Users AS usr
    INNER JOIN UserCTE AS mgr
      ON usr.managerId = mgr.userId where usr.managerId IS NOT NULL
)
SELECT * 
  FROM UserCTE AS u where u.ManagerId=3
  ORDER BY EmpLevel;

Output :

userName
--------
    Ani

The output that i am expecting is, if i give a ManagerId 3,then following employees should be shown

1.Abros
2.Ani
3.Raju
4.Pinky

Can anyone help on this

回答1:

Try this. Filter has to be applied in the Anchor query of CTE

WITH UserCTE
     AS (SELECT userId,
                userName,
                managerId,
                0 AS EmpLevel
         FROM   [Users]
         WHERE  managerId = 3
         UNION ALL
         SELECT usr.userId,
                usr.userName,
                usr.managerId,
                mgr.[EmpLevel] + 1
         FROM   [Users] AS usr
                INNER JOIN UserCTE AS mgr
                        ON usr.managerId = mgr.userId
         WHERE  usr.managerId IS NOT NULL)
SELECT *
FROM   UserCTE AS u
ORDER  BY EmpLevel;

FIDDLE DEMO

来源：https://stackoverflow.com/questions/27631884/recursive-cte-find-all-employees-below-manager

标签

sql

.net

sql-server

recursive-cte