Window Functions

Summary

Functions like ROW_NUMBER, RANK, and running totals that calculate across a set of rows related to the current row, without collapsing them the way GROUP BY does.

• 1Use ROW_NUMBER() to find the most recent order per customer.
• 2Practice a running total using SUM() OVER (ORDER BY ...).
• 3Learn the OVER (PARTITION BY ...) syntax — it's the key to most window function power.