Perfect! To count registrations in 2016, we use the following WHERE clause:

WHERE RegistrationDate >= '20160101'
  AND RegistrationDate <  '20170101';

There is also an alternative way of writing this query. Take a look:

SELECT COUNT(CustomerID) AS RegistrationCount2016
FROM Customers
WHERE RegistrationDate >= '20160101'
  AND RegistrationDate <  DATEADD(year, 1, '20160101');

This time, instead of providing the end date specifically, we used the DATEADD(interval, number, date) function. It takes three arguments:

1. interval – the interval we want to add, such as year or month.
2. number – the number of intervals to add.
3. date – the date to which the interval will be added.

In our example, DATEADD(year, 1, '20160101') means "add one year to the date of 1 January 2016".