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docs: update docs
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@ -57,8 +57,8 @@ export default defineConfig({
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text: '基础功能',
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items: [
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{text: '增、删、改', link: '/zh/base/add-delete-update'},
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{text: '查询（多表和分页）', link: '/zh/base/query'},
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{text: '一对多、多对一', link: '/zh/base/relations-query'},
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{text: '基础查询', link: '/zh/base/query'},
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{text: '关联查询', link: '/zh/base/relations-query'},
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{text: '批量操作', link: '/zh/base/batch'},
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{text: 'QueryWrapper', link: '/zh/base/querywrapper'},
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{text: 'Db + Row', link: '/zh/base/db-row'},
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@ -119,7 +119,7 @@ export default defineConfig({
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(function() {
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var hm = document.createElement("script");
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hm.src = "https://hm.baidu.com/hm.js?3f50d5fbe3bf955411748b5616b24a24";
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var s = document.getElementsByTagName("script")[0];
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var s = document.getElementsByTagName("script")[0];
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s.parentNode.insertBefore(hm, s);
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})();
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`
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@ -1,12 +1,12 @@
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# 一对多、多对一
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# 关联查询
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在 MyBatis-Flex 中，我们内置了 3 种方式，帮助用户进行关联查询，比如 `一对多`、`一对一`、`多对一`、`多对多`等场景，他们分别是：
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在 MyBatis-Flex 中，我们内置了 3 种方案，帮助用户进行关联查询，比如 `一对多`、`一对一`、`多对一`、`多对多`等场景，他们分别是：
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- Relations 注解
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- Field Query
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- Join Query
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- 方案1：Relations 注解
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- 方案2：Field Query
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- 方案3：Join Query
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## Relations 注解
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## 方案 1：Relations 注解
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在 MyBatis-Flex 中，提供了 4 个 Relations 注解，他们分别是：
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@ -18,11 +18,13 @@
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添加了以上配置的实体类，在通过 `BaseMapper` 的方法查询数据时，需要调用 select*****WithRelations**() 方法，Relations 注解才能生效。
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否则 MyBatis-Flex 自动忽略 Relations 注解。
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BaseMapper 提供的 withRelations 方法列表，详情点击[这里](/zh/base/query.html#relations-注解查询)。
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## 一对一 `@RelationOneToOne`
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假设有一个账户，账户有身份证，账户和身份证的关系是一对一的关系，代码如下所示：
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Account.java :
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Account.java :
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```java 8
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public class Account implements Serializable {
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@ -33,21 +35,21 @@ public class Account implements Serializable {
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@RelationOneToOne(selfField = "id", targetField = "accountId")
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private IDCard idCard;
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//getter setter
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}
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```
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IDCard.java :
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```java
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```java
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@Table(value = "tb_idcard")
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public class IDCard implements Serializable {
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private Long accountId;
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private String cardNo;
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private String content;
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//getter setter
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}
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```
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@ -57,7 +59,7 @@ public class IDCard implements Serializable {
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- **selfField** 当前实体类的属性
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- **targetField** 目标对象的关系实体类的属性
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> PS: 若 **selfField** 是主键，且当前表只有 1 个主键时，可以不填写。
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> PS: 若 **selfField** 是主键，且当前表只有 1 个主键时，可以不填写。因此，以上的配置可以简化为 `@RelationOneToOne(targetField = "accountId")`
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假设数据库 5 条 Account 数据，然后进行查询：
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@ -71,7 +73,7 @@ System.out.println(accounts);
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```sql
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SELECT `id`, `user_name`, `age` FROM `tb_account`
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SELECT `account_id`, `card_no`, `content` FROM `tb_idcard`
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SELECT `account_id`, `card_no`, `content` FROM `tb_idcard`
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WHERE account_id IN (1, 2, 3, 4, 5)
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```
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@ -79,10 +81,10 @@ WHERE account_id IN (1, 2, 3, 4, 5)
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```txt
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[
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Account{id=1, userName='孙悟空', age=18, idCard=IDCard{accountId=1, cardNo='0001', content='内容1'}},
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Account{id=2, userName='猪八戒', age=19, idCard=IDCard{accountId=2, cardNo='0002', content='内容2'}},
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Account{id=3, userName='沙和尚', age=19, idCard=IDCard{accountId=3, cardNo='0003', content='内容3'}},
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Account{id=4, userName='六耳猕猴', age=19, idCard=IDCard{accountId=4, cardNo='0004', content='内容4'}},
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Account{id=1, userName='孙悟空', age=18, idCard=IDCard{accountId=1, cardNo='0001', content='内容1'}},
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Account{id=2, userName='猪八戒', age=19, idCard=IDCard{accountId=2, cardNo='0002', content='内容2'}},
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Account{id=3, userName='沙和尚', age=19, idCard=IDCard{accountId=3, cardNo='0003', content='内容3'}},
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Account{id=4, userName='六耳猕猴', age=19, idCard=IDCard{accountId=4, cardNo='0004', content='内容4'}},
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Account{id=5, userName='王麻子叔叔', age=19, idCard=IDCard{accountId=5, cardNo='0005', content='内容5'}}
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]
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```
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@ -103,14 +105,14 @@ public class Account implements Serializable {
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@RelationOneToMany(selfField = "id", targetField = "accountId")
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private List<Book> books;
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//getter setter
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}
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```
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Book.java :
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```java
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```java
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@Table(value = "tb_book")
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public class Book implements Serializable {
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@ -118,7 +120,7 @@ public class Book implements Serializable {
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private Long id;
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private Long accountId;
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private String title;
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//getter setter
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}
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```
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@ -128,7 +130,7 @@ public class Book implements Serializable {
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- **selfField** 当前实体类的属性
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- **targetField** 目标对象的关系实体类的属性
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> PS: 若 **selfField** 是主键，且当前表只有 1 个主键时，可以不填写。
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> PS: 若 **selfField** 是主键，且当前表只有 1 个主键时，可以不填写。因此，以上的配置可以简化为 `@RelationOneToOne(targetField = "accountId")`
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@ -144,7 +146,7 @@ System.out.println(accounts);
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```sql
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SELECT `id`, `user_name`, `age` FROM `tb_account`
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SELECT `id`, `account_id`, `title`, `content` FROM `tb_book`
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SELECT `id`, `account_id`, `title`, `content` FROM `tb_book`
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WHERE account_id IN (1, 2, 3, 4, 5)
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```
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@ -154,7 +156,7 @@ WHERE account_id IN (1, 2, 3, 4, 5)
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假设一个账户有很多本书籍，一本书只能归属一个账户所有；账户和书籍的关系是一对多的关系，书籍和账户的关系为多对一的关系，代码如下：
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Account.java 一对多的配置:
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Account.java:
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```java 8
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public class Account implements Serializable {
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@ -163,9 +165,6 @@ public class Account implements Serializable {
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private String userName;
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@RelationOneToMany(selfField = "id", targetField = "accountId")
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private List<Book> books;
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//getter setter
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}
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```
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@ -180,10 +179,10 @@ public class Book implements Serializable {
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private Long id;
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private Long accountId;
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private String title;
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@RelationManyToOne(selfField = "accountId", targetField = "id")
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private Account account;
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//getter setter
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}
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```
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@ -193,7 +192,8 @@ public class Book implements Serializable {
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- **selfField** 当前实体类的属性
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- **targetField** 目标对象的关系实体类的属性
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> PS: 若 **targetField** 目标对象的是主键，且目标对象的表只有 1 个主键时，可以不填写。
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> PS: 若 **targetField** 目标对象的是主键，且目标对象的表只有 1 个主键时，可以不填写。因此，以上的配置可以简化为
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> `@RelationManyToOne(selfField = "accountId")`
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@ -225,7 +225,7 @@ public class Account implements Serializable {
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targetField = "id", joinTargetColumn = "role_id"
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)
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private List<Role> roles;
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//getter setter
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}
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```
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@ -239,13 +239,6 @@ public class Role implements Serializable {
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private Long id;
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private String name;
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@RelationManyToMany(
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joinTable = "tb_role_mapping",
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selfField = "id", joinSelfColumn = "role_id",
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targetField = "id", joinTargetColumn = "account_id"
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)
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private List<Account> accounts;
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//getter setter
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}
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```
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@ -259,8 +252,25 @@ public class Role implements Serializable {
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- joinTargetColumn 目标表和中间表的关系字段
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> 注意：selfField 和 targetField 配置的是类的属性名，joinSelfColumn 和 joinTargetColumn 配置的是中间表的字段名。
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>
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> 若 **selfField** 和 **targetField** 分别是两张关系表的主键，且表只有 1 个主键时，可以不填写。
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>
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> 若 **selfField** 和 **targetField** 分别是两张关系表的主键，且表只有 1 个主键时，可以不填写。因此，以上配置可以简化如下：
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```java {7-11}
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public class Account implements Serializable {
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@Id(keyType = KeyType.Auto)
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private Long id;
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private String userName;
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@RelationManyToMany(
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joinTable = "tb_role_mapping", // 中间表
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joinSelfColumn = "account_id",
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joinTargetColumn = "role_id"
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)
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private List<Role> roles;
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//getter setter
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}
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```
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## 父子关系查询
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@ -270,7 +280,7 @@ public class Role implements Serializable {
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CREATE TABLE `tb_menu`
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(
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`id` INTEGER auto_increment,
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`parent_id` INTEGER,
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`parent_id` INTEGER,
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`name` VARCHAR(100)
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);
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```
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@ -369,7 +379,7 @@ JSON 输出内容如下：
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## Field Query
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## 方案 2：Field Query
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以下是文章的 `多对多` 示例，一篇文章可能归属于多个分类，一个分类可能有多篇文章，需要用到中间表 `article_category_mapping`。
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@ -417,7 +427,7 @@ List<Article> articles = mapper.selectListByQuery(queryWrapper
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select * from tb_article where id >= 100;
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-- 以上 SQL 得到结果后，再执行查询分类的 SQL，如下：
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select * from tb_category where id in
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select * from tb_category where id in
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(select category_id from article_category_mapping where article_id = 100);
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select * from tb_category where id in
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@ -469,7 +479,7 @@ List<Article> articles = mapper.selectListByQuery(query
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这些不仅仅只适用于 `一对多`、`一对一`、`多对一`、`多对多`等场景。任何 `Article` 对象里的属性，需要二次查询赋值的，都是可以通过这种方式进行，比如一些统计的场景。
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## Join Query
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## 方案 3：Join Query
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Join Query 是通过 QueryWrapper 构建 `Left Join` 等方式进行查询，其原理是 MyBatis-Flex 自动构建了 MyBatis 的 `<resultMap>`
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，我们只需要关注 MyBatis-Flex 的 SQL 构建即可。
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