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

WHERE O.OrderDate >= '20170301' AND O.OrderDate < '20170401'

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

SELECT
  C.CustomerId,
  CompanyName,
  SUM(Amount) AS TotalRevenue 
FROM Orders O
JOIN Customers C
  ON O.CustomerId = C.CustomerId
WHERE O.OrderDate >= '20170301'
  AND O.OrderDate < DATEADD(Month, 1, '20170301')
GROUP BY C.CustomerId,
  CompanyName;

This time, instead of providing the specific end date, we used the DATEADD() function, which looks like this:

DATEADD(interval, number, date)

This function takes three arguments:

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

In our example, DATEADD(Month, 1, '20170301') means "add one month to March 1, 2017".