Deleting duplicate record in SQL Server

Question

I have written a query to remove duplicate records from a table

;WITH a as
(
SELECT Firstname,ROW_NUMBER() OVER(PARTITION by Firstname, empID ORDER BY Firstname) 
AS duplicateRecCount
FROM dbo.tblEmployee
)
--Now Delete Duplicate Records
DELETE FROM tblEmployee
WHERE duplicateRecCount > 1 

But I don't know where I went wrong it is saying

Invalid column name duplicateRecCount

Can someone help me?

Answer 1

You need to reference the CTE in the delete statement...

WITH a as
(
SELECT Firstname,ROW_NUMBER() OVER(PARTITION by Firstname, empID ORDER BY Firstname) 
AS duplicateRecCount
FROM dbo.tblEmployee
)
--Now Delete Duplicate Records
DELETE FROM a
WHERE duplicateRecCount > 1

Answer 2

 DELETE duplicates FROM
(SELECT ROW_NUMBER() OVER (PARTITION BY firstname, lastname, EMPNO, salary,dept  ORDER BY empno) cnt
 FROM tblEmp)  duplicates
WHERE duplicates.Cnt > 1