August 2022
Beginner to intermediate
436 pages
9h 43m
Korean
Content preview from SQL로 시작하는 데이터 분석
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35
1
장
SQL을 활용한 분석
저장되는
id
열이 있으며, 여기에는 새 레코드가 생성될 때마다 마지막에 생성된 레코드의 다
음 숫자 값이 자동으로 저장되거나 기본키 생성자에 의해 만들어진 알파벳 값이 저장됩니다.
여러 개의 열을 조합해 단 하나의 값을 갖는 행을 생성할 수도 있습니다. 이러한 열 조합을
복
합키
composite
key
또는
비즈니스키
business
key
라고 합니다. 예를 들어, 사람 데이터가 저장된 테이블
에서
first
_
name
,
last
_
name
,
birthdate
열을 조합해 한 사람을 가리키는 고유한 값을 만
듭니다.
person
_
id
나
social
_
security
_
id
도 고유 식별자
unique
identifier
로 사용될 수 있습니
다.
인덱스를 사용하면 테이블에서 특정 레코드를 더 빠르게 찾거나 해당 열에 대한
JOIN
을 더 빠
르게 수행할 수 있습니다. 인덱스는 적용된 필드의 값과 해당 값이 저장된 행을 가리키는 포인
터를 저장하며, 전체 테이블보다 크기가 작아 더 빠르게 읽을 수 있습니다. 주로 기본키가 인덱
스인 경우가 많지만 다른 필드나 필드 그룹도 인덱스가 될 수 있습니다. 행 기반 데이터베이스
를 사용할 때 테이블에서 어떤 필드가 인덱스를 갖고 있는지 미리 알면 분석에 유용합니다. 인
덱스를 추가하면
JOIN
을 더 빠르게 수행할 ...
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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.