Perfect! When we wanted to find orders from March 2017, we used the following WHERE clause:

WHERE o.order_date >= '2017-03-01' AND o.order_date < '2017-04-01'

There is another way to write this query. Take a look:

SELECT
  c.customer_id,
  company_name,
  SUM(amount) AS total_revenue 
FROM orders o
JOIN customers c
  ON o.customer_id = c.customer_id
WHERE o.order_date >= '2017-03-01'
AND o.order_date < CAST('2017-03-01' AS DATE) + INTERVAL '1' month
GROUP BY c.customer_id, company_name;

This time, instead of providing the specific end date, we used the INTERVAL keyword:

CAST(date AS DATE) + INTERVAL 'number' interval

where:

1. interval – the interval we want to add, such as year, month or day.
2. number – the amount of that interval to add.
3. date – the date to be modified.

In our example, CAST('2017-03-01' AS DATE) + INTERVAL '1' month means "add one month to March 1, 2017".