Window Functions

Summary

Functions like ROW_NUMBER, RANK, and running totals that calculate across a set of related rows without collapsing them the way GROUP BY does — extremely useful for building time-aware features.

• 1Use ROW_NUMBER() to find the most recent event per user.
• 2Practice a running total or moving average using SUM()/AVG() OVER (ORDER BY ...).
• 3Learn PARTITION BY — the key to most window function power.