Yes, the solution by @JCorcuera is applicable, but I suggest applying a little more information to Rails to fulfill our requirement. Try this approach:
rails generate migration add_columnname_to_tablename columnname:datatype
For example:
rails generate migration add_password_to_users password:string
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…