Change column datatype in Oracle table (ALTER TABLE)

I had to change my column from USER_ID NUMBER(22) to USERNAME VARCHAR2 (20 BYTE)Oracle does not allow to modify column when there is data in the table. Also, you can not rename the column.

Finally I came up with the following script:

1. ALTER TABLE: add new column (USERNAME) with desired datatype.
2. UPDATE: copy data to the new column
   
3. ALTER TABLE: drop the original column (USER_ID)
   

I heard you can rename a column in Ms SQL.