DISTINCT operator is not allowed in the recursive part of a recursive common table expression '%.*ls'.

Error Message:
Msg 460, Level 16, State 1, Line 1
DISTINCT operator is not allowed in the recursive part of a recursive common table expression ‘%.*ls’.

Severity level:
16.

Description:
This error message appears when you try to use the DISTINCT operator in the recursive part of a Common Table Expression.

Consequences:
The T-SQL statement can be parsed, but causes the error at runtime.

Resolution:
Error of the Severity Level 16 are generated by the user and can be fixed by the SQL Server user. The statement cannot be executed this way. The DISTINCT operator must be removed.

Versions:
This error message was introduced with SQL Server 2005.

Example(s):
USE tempdb;
GO
IF OBJECT_ID(‘tempdb..#t’) > 0
 DROP TABLE #t
GO
CREATE TABLE #t
(
 id INT,
 reportToID INT NULL,
)
INSERT INTO #t SELECT 1, NULL
UNION ALL SELECT 2, 1
UNION ALL SELECT 3, 1
UNION ALL SELECT 4, 2

GO
WITH MyCTE (id, reportToID, Level)
AS
(
 SELECT t1.ID, t1.reportToID, 0 AS Level
   FROM #t AS t1
  WHERE reportToID IS NULL
  UNION ALL
 SELECT DISTINCT t1.ID, t1.reportToID, t2.Level + 1
   FROM #t AS t1
   JOIN MyCTE AS t2
     ON t1.reportToID = t2.ID
)
SELECT *
  FROM MyCTE
GO

Remarks:
In the above example we try to use the DISTINCT operator in the recursive part of a Common Table Expression. This raises the error.

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