SQL Window Functions Cheatsheet Practice Exam

SUM(amount) OVER (PARTITION BY user_id ORDER BY ts ROWS UNBOUNDED PRECEDING)

ROW_NUMBER: unique sequential.
RANK: same value → same rank, leaves gaps.
DENSE_RANK: same value → same rank, no gaps.

SELECT * FROM (
  SELECT *, ROW_NUMBER() OVER (PARTITION BY group_id ORDER BY score DESC) rn
  FROM t
) x WHERE rn <= 3;

LAG(price) OVER (PARTITION BY symbol ORDER BY ts)

LEAD(price) OVER (PARTITION BY symbol ORDER BY ts)