README.md · AdamSun/mybatis-plus-join

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<h1 align="center">MyBatis-Plus-Join</h1>

 为简化开发工作、提高生产率而生


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对 <a href="https://github.com/baomidou/mybatis-plus" target="_blank">MyBatis-Plus</a> 多表查询的扩展 |
<a href="https://github.com/yulichang/mybatis-plus-join-demo" target="_blank">演示工程</a> |
<a href="https://mybatis-plus-join.github.io" target="_blank">使用文档</a> |
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### <a href="https://mybatis-plus-join.github.io" target="_blank">使用文档WIKI</a>

## 使用方法

### 安装

- Maven
 ```xml
 <dependency>
 <groupId>com.github.yulichang</groupId>
 <artifactId>mybatis-plus-join-boot-starter</artifactId>
 <version>1.4.13</version>
 </dependency>
 ```
- Gradle
 ```
 implementation 'com.github.yulichang:mybatis-plus-join-boot-starter:1.4.13'
 ```
 或者clone代码到本地执行 mvn install, 再引入以上依赖 
 
 注意: MyBatis Plus版本需要3.3.0+

### 使用

* mapper继承MPJBaseMapper

### Lambda形式用法（MPJLambdaWrapper）

#### 简单的连表查询

```java
class test {
    @Resource
    private UserMapper userMapper;

void testJoin() {
 //和Mybatis plus一致，MPJLambdaWrapper的泛型必须是主表的泛型，并且要用主表的Mapper来调用
 MPJLambdaWrapper<UserDO> wrapper = JoinWrappers.lambda(UserDO.class)
 .selectAll(UserDO.class)//查询user表全部字段
 .select(UserAddressDO::getTel)//查询user_address tel 字段
 .selectAs(UserAddressDO::getAddress, UserDTO::getUserAddress)//别名
 .select(AreaDO::getProvince, AreaDO::getCity)
 .leftJoin(UserAddressDO.class, UserAddressDO::getUserId, UserDO::getId)
 .leftJoin(AreaDO.class, AreaDO::getId, UserAddressDO::getAreaId)
 .eq(UserDO::getId, 1)
 .like(UserAddressDO::getTel, "1")
 .gt(UserDO::getId, 5);

//连表查询 返回自定义ResultType
 List<UserDTO> list = userMapper.selectJoinList(UserDTO.class, wrapper);

//分页查询 （需要启用 mybatis plus 分页插件）
 Page<UserDTO> listPage = userMapper.selectJoinPage(new Page<>(2, 10), UserDTO.class, wrapper);
 }
}
```

对应sql

```
SELECT  
    t.id, t.name, t.sex, t.head_img, 
    t1.tel, t1.address AS userAddress,
    t2.province, t2.city 
FROM 
    user t 
    LEFT JOIN user_address t1 ON t1.user_id = t.id 
    LEFT JOIN area t2 ON t2.id = t1.area_id 
WHERE (
    t.id = ? 
    AND t1.tel LIKE ? 
    AND t.id > ?)
```

MPJLambdaWrapper其他功能

* <a href="https://mybatis-plus-join.github.io/pages/core/lambda/select/selectCollection.html" target="_blank">
 一对一，一对多使用</a>
* <a href="https://mybatis-plus-join.github.io/pages/core/lambda/select/selectFunc.html" target="_blank">简单的SQL函数使用</a>
* <a href="https://mybatis-plus-join.github.io/pages/core/lambda/join/leftJoin.html" target="_blank">ON语句多条件支持</a>
* <a href="https://mybatis-plus-join.github.io" target="_blank">其他全部功能请参考使用文档</a>

# <a href="https://mybatis-plus-join.github.io" target="_blank">使用文档 wiki</a>
# 用爱发电
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AdamSun/mybatis-plus-join

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