Primary key is always unique in every SQL. You dont have to explicitly define it as UNIQUE.
On a side note: You can only have onePrimary key in a table and it never allows null values. Also you can have only one primary key constraint in the table(as the point of creating a primary key is to uniquely identify the row in your table) but you can more than one unique key constraint in your table.
Example:
An employee details table having EmpID as Primary key and EmpPhoneNo as unique key.