Over the column v with values 10, 10, 20, the two queries below compute a running total. What totals does the first row with v=10 versus the second row with v=10 get from the default-frame version, and how does that differ from the ROWS version?
SELECT v,
sum(v) OVER (ORDER BY v) AS default_frame,
sum(v) OVER (ORDER BY v
ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS rows_frame
FROM (VALUES (10),(10),(20)) t(v);