"""""""""
Suppose you work for a retail company that has a database containing two tables, 
one called 'orders', and one called 'revenue', as shown below:
Orders:
    order_id	channel	    date	    month
0	    1	    Online	    2018-09-01	September
1	    2	    Online	    2018-09-03	September
2	    3	    In_store	2018-10-11	October
3	    4	    In_store	2018-08-21	August
4	    5	    Online	    2018-08-13	August
5	    6	    Online	    2018-10-29	October

Revenue:
    order_id	revenue
0	1	        100
1	2	        125
2	3	        200
3	4	        80
4	5	        200
5	6	        100
Using SQL, write a query to show the total revenue by channel for the months of September and October. 
Additionally, try to think of the most efficient way to run this query.
"""

