Join이란?
테이블간의 관계 성에 따라 복수의 테이블을 결합하여, 하나의 테이블인 것처럼 결과를 출력하는 것
Join의 종류
Data
CREATE TABLE `testdb`.`person` (
`id` INT NOT NULL,
`name` VARCHAR(45) NULL,
`job_id` INT NULL,
PRIMARY KEY (`id`));
INSERT INTO person values(1,'personA',1);
INSERT INTO person values(2,'personB',2);
INSERT INTO person values(3,'personC',3);
INSERT INTO person values(4,'personD',4);
CREATE TABLE `testdb`.`job` (
`id` INT NOT NULL,
`job_name` VARCHAR(45) NULL,
PRIMARY KEY (`id`));
INSERT INTO job values(1,'직장인');
INSERT INTO job values(2,'학생');
INSERT INTO job values(3,'무직');
INSERT INTO job values(5, '군인');
INNER JOIN
Query
SELECT P.id, name, J.job_name FROM person P INNER JOIN job J ON P.job_id = J.id;
OUTTER JOIN
1. LEFT JOIN
Query
SELECT P.id, name, J.job_name FROM person P LEFT JOIN job J ON P.job_id = J.id;
2. RIGHT JOIN
Query
SELECT P.id, name, J.job_name FROM person P RIGHT JOIN job J ON P.job_id = J.id;
LEFT JOIN과 RIGHT JOIN의 차이