One thing that confused me when I first started learning ClickHouse was the word FINAL . Because eventually you'll come across both: SELECT * FROM events FINAL ; and: OPTIMIZE TABLE events FINAL ; At first glance, they sound like they should do roughly the same thing. After all, both contain the word FINAL . But they actually solve two completely different problems. One affects query results. The other affects how data is physically stored. Understanding this distinction can save a lot of confus