Question

Here is my CTE – it is causing an error. Help me to figure out the error

CREATE TABLE [dbo].[myEmpTab](
[EMPNO] [int] NULL,
[ENAME] [varchar](10)  NULL,
[JOB] [varchar](20)  NULL,
[MGR] [int] NULL,
[HIREDATE] [datetime] NULL,
[SAL] [int] NULL
) ON [PRIMARY]

;
WITH MyCTE AS 
( 
  SELECT EMPNO, EName, Null as MGR, NULL as ManagerName
  FROM myEmpTab
  WHERE MGR IS NULL
  UNION ALL
  SELECT  EMPNO, EName, MGR, MyCTE.EName
  FROM myEmpTab
  INNER JOIN MyCTE ON myEmpTab.MGR = MyCTE.EMPNO
  WHERE myEmpTab.MGR IS NOT NULL 
)
SELECT * FROM MyCTE

when i am executing the sql then i am getting error like

Msg 209, Level 16, State 1, Line 8
Ambiguous column name 'EMPNO'.
Msg 209, Level 16, State 1, Line 8
Ambiguous column name 'EName'.
Msg 209, Level 16, State 1, Line 8
Ambiguous column name 'MGR'.

i am not being able to catch the error . so please anyone have a lot and help me to fix it. thanx.

Answer 1

I don’t think you can reference a CTE inside itself. Try this

WITH MyCTE AS 
( 
SELECT EMPNO, EName, MGR, Sal
FROM myEmpTab
WHERE MGR IS NULL
)

SELECT EMPNO, EName, MGR, Sal FROM MyCTE

UNION ALL

SELECT  e.EMPNO, e.EName, e.MGR, MyCTE.EName
FROM myEmpTab e
INNER JOIN MyCTE ON e.MGR = MyCTE.EMPNO
WHERE e.MGR IS NOT NULL 

OR

WITH MyCTE AS 
( 
    SELECT EMPNO, EName, MGR, Sal
    FROM myEmpTab
    WHERE MGR IS NULL
),
MyCTE2 as
(
    SELECT EMPNO, EName, MGR, Sal FROM MyCTE

    UNION ALL

    SELECT  e.EMPNO, e.EName, e.MGR, MyCTE.EName
    FROM myEmpTab e
    INNER JOIN MyCTE ON e.MGR = MyCTE.EMPNO
    WHERE e.MGR IS NOT NULL 
)
SELECT * FROM MyCTE2