Frame clauses: how many rows does 1 PRECEDING cover?

Question

Accepted Answer

ROWS BETWEEN 1 PRECEDING AND CURRENT ROW defines a frame that includes the previous row and the current row - exactly 2 rows. Day 1: only 1 row in frame (no predecessor) -> 10. Day 2: 10+20=30. Day 3: 20+30=50. Day 4: 30+40=70. Frame clauses give you precise control: UNBOUNDED PRECEDING gives a running total, 1 PRECEDING gives a rolling window, CURRENT ROW gives a single-row aggregate.