I feel like window functions are the most difficult topic in SQL. At the same time, it’s the most powerful one and I’m really glad we’ve met window functions many times in the course. Let’s review them:
ROW_NUMBER() function gives each record in the partition a number (starting with 1 ). We used it for marketing attribution by looking at the URL of the first pageview for each user:
SELECT ROW_NUMBER() OVER(PARTITION BY visitor_id ORDER BY created_at ASC) AS pageview_number, * FROM web_analytics.pageviews
LAG(column, offset = 1)...
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.