select
first_value(b) over (partition by a order by b)...
는 아래와 동일
select
first_value(b) over (partition by a order by b
ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
select last_value(b) over (partition by a order by b)...
는 아래와 동일
select
last_value(b) over (partition by a order by b
ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)
last_value 사용시에는 주의하세요. 오늘에서야 알았네요 --;
오라클도 동일합니다
