the last page people visit before coming to the homepage? ➔ What are all the product pages people see after the homepage? ➔ How many people who visit the homepage go on to buy something? ➔ What if we limit that to buy within two days?
migrated to station 1 then station 3 before station 2? ➔ What drugs did people take in the last month before starting drug X? ➔ What was the last ad clicked before registering? ➔ What companies had their stock hit $100 per share then drop to $40?
their first registration afterward? 1. Filter landed for the first row per user 2. Left join with registered on user_id 3. Filter for timestamp.y > timestamp.x or NA 4. Filter for first row of timestamp.y