[MySQL] INNER, LEFT, RIGHT JOIN 정리

Database2 - Mysql

2020-03-23
2nd day

---

JOIN

topic 테이블 ↓

id	title	description	created	author_id
1	MySQL	MySQL is...	2018-01-01 12:10:11	1
2	Oracle	Oracle is...	2018-01-03 13:01:10	1
3	SQL Server	SQL Server is...	2018-01-20 11:01:10	2
4	PostgreSQL	PostgreSQL is...	2018-01-23 01:03:03	3
5	MongoDB	MongoDB is...	2018-01-30 12:31:03	1

 

author 테이블 ↓

id	name	profile
1	egoing	developer
2	duru	data administrator
3	taeho	data scientist, developer

 

author_id와 author.id를 일치시키기 위해 아래 쿼리 실행

SELECT topic.id AS 'topic.id', -- AS : 이름지정
       title, 
       description, 
       created, 
       name, 
       profile 
       FROM topic 
       LEFT JOIN author -- INNER, LEFT, RIGHT 등등.. 벤다이어그램을 생각
       ON topic.author_id=author.id; -- topic테이블과 author테이블의 공통 키값을 기준으로 한다.

 

결과물

topic.id	title	description	created	name	profile
1	MySQL	MySQL is...	2018-01-01 12:10:11	egoing	developer
2	Oracle	Oracle is...	2018-01-03 13:01:10	egoing	developer
5	MongoDB	MongoDB is...	2018-01-30 12:31:03	egoing	developer
3	SQL Server	SQL Server is...	2018-01-20 11:01:10	duru	data administrator
4	PostgreSQL	PostgreSQL is...	2018-01-23 01:03:03	taeho	data scientist, developer

 

참고 이미지

INNER JOIN

LEFT, RIGHT JOIN

Link

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