SQL window function previewer: PARTITION BY visualizer

Window functions confuse people because the table does not shrink. This is five rows you can re-rank. No server, no SQL to run — the idea, on a grid.

PARTITION BY restarts the numbering. ORDER BY decides who is 1. SUM() OVER keeps every row and adds as it goes. That is the whole lecture. Write it for real on ROW_NUMBER and running totals.