How to query by month?

Hi all,

im a beginner for SQL, and  trying to use it with my daily work.

Now i catched this question(my title of mail).

Suppose there is a table about orders, i want to sum the total amount of each month.

There was a statement of mine to november.

select  sum(order_amount) FROM table_name WHERE order_date between '2016-11-01' AND '2016-11-30';

I know it comes a result what i want, but i hope someone can tell me another way to use.

After searched, i found  there is a function named date_part, but it doesn't work.

thanks for any help!

Leopold