Who issues SQL queries?
SELECTfiltered by date and user. They would need to figure out how to insert data and update it (which we'll discuss much later)
SELECTstatements, because they need to do very complex queries to do the analysis they're interested in. For example, they might use a
SELECTto analyze what percentage of users were more likely to do more exercise if they started off exercising in the morning, maybe using
SELECTto look at how many users even use the "heart_rate" field at all, if they're debating getting rid of it.