Bindle founders received an email from the VC firm asking to share their cumulative revenues per country. The first instinct was to open Excel or Google Spreadsheets and go “old school”. But that’s an old habit. Let’s find out how to work with cumulative aggregates in SQL 
Aggregated values are not a new concept for us. They are the result of applying grouping and counting or grouping and summing techniques. Here’s a query that gives us revenue per country per month:
SELECT country, DATE_TRUNC('month', p.created_at), SUM(amount) FROM purchases...
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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. 