@ManyToOne(optional=false)/@JoinColumn(nullable=false)

MEMBER,TEAM.txt

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Team

@Getter
@Setter
@Builder
@AllArgsConstructor
@NoArgsConstructor
@Entity
class Team {
	@Id
	private Integer id;
	private String name;

	@OneToMany(mappedBy = "team")
	private List<Member> member;
}

 

Member

@Getter
@Setter
@Builder
@AllArgsConstructor
@NoArgsConstructor
@Entity
class Member {
	@Id
	private Integer id;
	private String name;

	@ManyToOne
	@JoinColumn(name = "team_id")
	private Team team;
}

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1. 기본

 

create시 fk 컬럼인 team_id에 not null제약이 걸리지 않는다.

 

다음의 쿼리를 통해 테스트 데이터 insert후 join을 비교해보면

create table member (id integer not null, name varchar(255), team_id varchar(255), primary key(id));
create table team (id integer not null, name varchar(255), primary key(id));
alter table member add constraint member_team_id_fk foreign key (team_id) references team(id);
insert into team values(1, 'team1');
insert into team values(2, 'team2');
insert into team values(3, 'team3');
insert into member values(1, 'mem1', null);
insert into member values(2, 'mem2', null);
insert into member values(3, 'mem3', null);
insert into member values(4, 'mem4', null);
insert into member values(5, 'mem5', null);
insert into member values(6, 'mem6', null);
insert into member values(7, 'mem7', null);
insert into member values(8, 'mem8', null);
insert into member values(9, 'mem9', null);
insert into member values(10, 'mem10', null);
insert into member values(11, 'mem11', null);
insert into member values(12, 'mem12', null);
insert into member values(13, 'mem13', null);
insert into member values(14, 'mem14', null);
insert into member values(15, 'mem15', null);
update member set team_id = 1 where id  in (1,2,3,4,5);
update member set team_id = 2 where id  in (6,7,8,9,10);

 

위와 같이 fk컬럼이 null인 경우도 존재하므로 left join(left outer join)을 사용해서 값을 가져온다고 한다.

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2. 둘중 하나이상 false로 설정된 경우

@ManyToOne(optional = false)
@JoinColumn(name = "team_id")
//또는
@ManyToOne
@JoinColumn(name = "team_id", nullable = false)
//또는
@ManyToOne(optional = false)
@JoinColumn(name = "team_id", nullable = false)
private Team team;

 

create시 fk컬럼에 not null제약이 걸린다.

 

fk컬럼이 null인 경우가 없으므로 inner join(left inner join)을 통해 값을 가져온다고 한다.

또한 Member객체 team필드 미셋팅 상태로 persist시 에러가 발생

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https://feco.tistory.com/102

NULL 제약 조건과 조인 전략