mirror of
https://gitee.com/best_handsome/mybatis-plus-join
synced 2025-07-11 00:02:22 +08:00
139 lines
4.0 KiB
Markdown
139 lines
4.0 KiB
Markdown
# mybatis-plus-join
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支持连表查询的[mybatis-plus](https://gitee.com/baomidou/mybatis-plus)
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[goto gitee](https://gitee.com/best_handsome/mybatis-plus-join)
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## 运行环境
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* mysql8
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* jdk8
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* mybatis-plus 3.4.2
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## 使用方法
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### 使用
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* entity继承MyBaseEntity
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* mapper继承MyBaseMapper
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* service继承MyBaseService
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* serviceImpl继承MyBaseServiceImpl
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### MyLambdaQueryWrapper用法
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#### select(UserEntity::getId) 查询指定的字段,支持可变参数
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查询user表中的head_img,name和user_address表中的address,tel
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```java
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class test {
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void testJoin() {
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List<UserDTO> list = userMapper.selectJoinList(new MyLambdaQueryWrapper<UserEntity>()
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.select(UserEntity::getHeadImg, UserEntity::getHeadImg)
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.leftJoin(UserEntity::getId, UserAddressEntity::getUserId,
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right -> right.select(UserAddressEntity::getAddress, UserAddressEntity::getTel))
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, UserDTO.class);
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}
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}
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```
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对应sql
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```sql
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SELECT t0.head_img, t0.head_img, t1.address, t1.tel
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FROM user t0
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LEFT JOIN user_address t1 ON t0.id = t1.user_id
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```
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#### selectAll(UserEntity.class) 查询UserEntity全部字段
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查询user全部字段和user_address表中的address,tel
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```java
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class test {
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@Resource
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private UserMapper userMapper;
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void testJoin() {
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List<UserDTO> list = userMapper.selectJoinList(new MyLambdaQueryWrapper<UserEntity>()
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.selectAll(UserEntity.class)
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.leftJoin(UserEntity::getId, UserAddressEntity::getUserId,
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right -> right.select(UserAddressEntity::getAddress, UserAddressEntity::getTel))
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, UserDTO.class);
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}
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}
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```
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对应sql
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```sql
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SELECT t0.name, t0.sex, t0.head_img, t0.id, t1.address, t1.tel
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FROM user t0
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LEFT JOIN user_address t1 ON t0.id = t1.user_id
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```
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#### as(UserEntity::getHeadImg,UserDTO::getUserHeadImg)
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查询字段head_img as userHeadImg
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```java
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class test {
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@Resource
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private UserMapper userMapper;
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void testJoin() {
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List<UserDTO> list = userMapper.selectJoinList(new MyLambdaQueryWrapper<UserEntity>()
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.as(UserEntity::getHeadImg, UserDTO::getUserHeadImg)
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.leftJoin(UserEntity::getId, UserAddressEntity::getUserId,
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right -> right.select(UserAddressEntity::getAddress, UserAddressEntity::getTel))
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, UserDTO.class);
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}
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}
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```
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对应sql
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```sql
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SELECT t0.head_img AS userHeadImg, t1.address, t1.tel
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FROM user t0
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LEFT JOIN user_address t1 ON t0.id = t1.user_id
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```
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#### 左连接 leftJoin(UserEntity::getId,UserAddressEntity::getUserId,right -> right)
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前连个参数是两个表的连接条件:
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user left join user_address on user.id = User_address.user_id
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第三个参数是右表wrapper对象,可以继续使用,以上方法.
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#### 条件查询eq()
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```java
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class test {
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@Resource
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private UserMapper userMapper;
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void testJoin() {
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List<UserDTO> list = userMapper.selectJoinList(new MyLambdaQueryWrapper<UserEntity>()
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.selectAll(UserEntity.class)
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.leftJoin(UserEntity::getId, UserAddressEntity::getUserId,
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right -> right.select(UserAddressEntity::getAddress, UserAddressEntity::getTel))
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.eq(true, UserEntity::getId, 1)
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.like(UserAddressEntity::getTel, "1")
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.eq(UserEntity::getId, UserAddressEntity::getUserId)
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, UserDTO.class);
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}
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}
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```
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对应sql
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```sql
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SELECT t0.name, t0.sex, t0.head_img, t0.id, t1.address, t1.tel
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FROM user t0
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LEFT JOIN user_address t1 ON t0.id = t1.user_id
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WHERE (t0.id = ? AND t1.tel LIKE ? AND t0.id = t1.user_id)
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```
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#### [参考测试类](https://gitee.com/best_handsome/mybatis-plus-join/blob/master/src/test/java/com/example/mp/MpJoinTest.java)
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