August 2022
Beginner to intermediate
436 pages
9h 43m
Korean
Content preview from SQL로 시작하는 데이터 분석
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149
3
장
시계열 분석
이렇듯 테이블이 필요한 날짜 데이터를 포함한다면, 어떤 값을 저장하든 상관없이 날짜 차원
테이블처럼 활용할 수 있습니다.
지금까지
SQL
에서 카티션
JOIN
을 활용해 희소 데이터의 시간 윈도우 롤링을 계산하는 방법을
알아봤습니다. 다음으로, 분석에서 자주 사용되는 누적값 계산을 알아봅시다.
3.4.3
누적값 계산
지난 예제에서 윈도우 크기를
12
개월로 설정했듯, 이동 평균 등의 윈도우 롤링 계산 시 윈
도우 크기를 고정된 값으로 설정하는 것이 일반적입니다. 이동 계산 외에도
YTD
year
-
to
-
date
,
QTD
quarter
-
to
-
date
,
MTD
month
-
to
-
date
등의 ‘누적값’을 활용해 시계열을 분석하는 방법도 있습니
다. 누적값은 크기가 고정된 윈도우를 사용하되 시작 포인트부터 점점 윈도우 크기를 늘려가며
계산을 수행합니다.
누적값 계산에는 윈도우 함수를 사용하면 가장 간단합니다. 다음 예제 코드는
sum
집계 함수를
사용해 총 매출
YTD
를 계산합니다(그 외에도 월 평균
YTD
를 구하려면
avg
집계 함수를, 월
최대
YTD
를 구하려면
max
집계 함수를 사용하면 됩니다).
PARTITION
BY
절로 윈도우를 설
정하는데, 예제에서는
sales
_
month
의 연도를 기준으로 설정합니다. 시계열 분석에서는 주로
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.