SQL Server deletes duplicate rows

Code
Create   Table Table1
(
ID Int   Identity ( 1 , 1 ) Primary   Key ,
Col1 Char ( 5 ),
Col2 Datetime ,
Col3 Int
)

-- Filter out duplicate data (the IDs are different, and other columns are the same)
With A As
(
Select Row_number () Over ( Order   By ID Desc ) As Rownumber, table1. *
From Table1
),
B As
(
Select   Min (Rownumber) As Minrow From A
Group   By Col1, col2, col3
)
Select ID,. * , B. minrow

from A left outer join B On . rownumber = B. minrow
where B. minrow is null