SQL Server – Generate Row Number in Select and Select into

How to Generate the Row Number in Select and Select into script?

Using IDENTITY for Select Into

SELECT RowNumber=IDENTITY(int,1,1),FIRST_NAME,LAST_NAME 
into EMPLOYEE_backup FROM EMPLOYEE

Using Row_Number() for Select

SELECT ROW_NUMBER() OVER (ORDER BY ID ASC) RowNumber,
FIRST_NAME,LAST_NAME FROM EMPLOYEE

Using Row_Number() for Select into

SELECT ROW_NUMBER() OVER (ORDER BY ID ASC) RowNumber ,
FIRST_NAME,LAST_NAME into EMPLOYEE_backup1 FROM EMPLOYEE