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Introduction
Customer registration
Customer cohorts
Summary

## Instruction

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".

## Exercise

Modify the template which contains the query from the previous exercise, so that it uses the DATEADD() function. (We want to see the first half of the year 2017.)

### Stuck? Here's a hint!

Use the following invocation:

DATEADD(month, 6, '20170101')