1、一对一 (One to One)
共三种情况:
1.1 主键共享
1.2
外键共享
1.3 中间表关联
1.1 code:
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@Entitypublic class article {
@Id
@GeneratedValue
public
Integer getArticleId() {
return
articleId;
}
.....
@OneToOne(cascade=CascadeType.ALL)
@PrimaryKeyJoinColumn
public
articleContent getContent() {
return
content;
}
......
} |
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@Entitypublic class articleContent {
@Id
@GeneratedValue
public
Integer getcId() {
return
cId;
}
....
} |
执行保存 生成两张无外键的独立表
1.2 code:
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@Entitypublic class article {
@OneToOne(cascade=CascadeType.ALL)
@JoinColumn(name="cid_fk")
public
articleContent getContent() {
return
content;
}
}@Entitypublic
class articleContent {
@OneToOne(mappedBy="articleContent")
public
article ArticleEntity;
} |
执行保存，生成两张表，同时article生成一个cid_fk字段 关联 articleContent主键ID
1.3 code:
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@Entitypublic class article {
@Id
@GeneratedValue
public
Integer getArticleId() {
return
articleId;
}
@OneToOne(cascade=CascadeType.ALL)
@JoinTable(name="article_content",
joinColumns=@JoinColumn(name="aid"),
inverseJoinColumns=@JoinColumn(name="aid_fk"))
public
articleContent getContent() {
return
content;
}
......
} |
生成三张表 分别为：article，article_content，articlecontent 其中 article_content 分别生成两个外键具体参考等价建表语句：
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CREATE TABLE `article_content` (
`aid_fk` int(11) DEFAULT
NULL,
`aid` int(11) NOT
NULL,
PRIMARY
KEY (`aid`),
KEY
`FK_7pgn2vn8r1lpswmh5v2ix667s` (`aid_fk`),
CONSTRAINT
`FK_ebfc4cs1sishg6u8kwpvgqqj9` FOREIGN
KEY (`aid`) REFERENCES
`article` (`articleId`),
CONSTRAINT
`FK_7pgn2vn8r1lpswmh5v2ix667s` FOREIGN
KEY (`aid_fk`) REFERENCES
`articlecontent` (`cId`)
) ENGINE=InnoDB DEFAULT
CHARSET=utf8;
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