Let’s look at the most popular window functions.
SUM(), AVG(), COUNT(), MIN(), MAX()
These 5 are referred to as aggregate window functions. We’ve already seen these functions when we were working with GROUP BY
.
SUM()
or COUNT()
are great when we need to calculate percentage of a row value to a total. For example here’s a query that calculates revenue per country and also percentage from total revenue of the company:
WITH revenue_per_country AS ( SELECT country, SUM(amount) AS country_revenue FROM purchases p INNER JOIN users u ON p.user_id = u.id...
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About SQL Habit
Hi, it’s Anatoli, the author of SQL Habit. 
SQL Habit is a course (or, as some of the students say, “business simulator”). It’s based on a story of a fictional startup called Bindle. You’ll play a role of their Data Analyst
and solve real-life challenges from Business, Marketing, and Product Management.
SQL Habit course is made of bite-sized lessons (you’re looking at one atm) and exercises. They always have a real-life setting and detailed explanations. You can immediately apply everything you’ve learned at work. 