Marking rows in an SQL Server table as duplicates

Have you got duplicate rows in your data? Here's how you are can find them and mark them as duplicate.
My SQL Server Udemy courses are:
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In this video, we will create a new table with two columns - "name" and ID.
We will then find where a "name" has been used for more than once, and then mark them as duplicates.
You can then review them and manipulate them as you want.
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Here is the code for this video:
SELECT *

DROP TABLE IF EXISTS tblColumns
GO

SELECT [name], ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) AS ID
INTO tblColumns
FROM

WITH myTable AS
(
SELECT *, ROW_NUMBER() OVER(PARTITION BY [name] ORDER BY ID) - 1 AS RowNumbers
FROM tblColumns
)
SELECT *
FROM myTable
WHERE RowNumbers != 0

SELECT *, ROW_NUMBER() OVER(PARTITION BY [name] ORDER BY ID) - 1 AS RowNumbers
FROM tblColumns

ALTER TABLE tblColumns
ADD IsDuplicate INT

UPDATE tblColumns
SET IsDuplicate = ROW_NUMBER() OVER(PARTITION BY [name] ORDER BY ID) - 1

WITH myTable AS
(
SELECT *, ROW_NUMBER() OVER(PARTITION BY [name] ORDER BY ID) - 1 AS RowNumbers
FROM tblColumns
)
UPDATE myTable
SET IsDuplicate = RowNumbers

SELECT * FROM tblColumns
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Links to my website are:

[qasimawan]

You are a brilliant teacher Phillip! Thanks for the video and awesome courses on Udemy!