How do I duplicate a column in a SQL Table?

I am using SQL Server 2014 and I have a table named Table1. Assuming I want to duplicate a column named SubCategory into a new column called SubCategory2 (with the same values as in column SubCategory), what would be the SQL syntax to do this?

Note: Idea here is to keep column Subcategory but create another column SubCategory2 and modify some specific values in that new column.

Example (assuming Table1 has only 2 columns):

Serial  Subcategory
  1        UK
  2        UK
  3        FR
  4        DE

Expected output:

Serial  Subcategory  Subcategory2
  1        UK           UK
  2        UK           UK
  3        FR           FR
  4        DE           DE

Answer

A combination of Add a column with a default value to an existing table in SQL Server and How can I copy data from one column to another in the same table? woold look something like:

ALTER TABLE Table1
ADD SubCategory2 {Type of subcategory 1} {NULL|NOT NULL} 
UPDATE Table1 SET SubCategory2 = SubCategory;