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https://gitee.com/best_handsome/mybatis-plus-join
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README.md
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README.md
@ -2,12 +2,6 @@
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支持连表查询的[mybatis-plus](https://gitee.com/baomidou/mybatis-plus)
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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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### 方法一
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@ -47,6 +41,7 @@
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## MyQuery用法
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### 简单的3表查询
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```java
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class test {
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@Resource
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@ -72,16 +67,14 @@ class test {
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对应sql
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```sql
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SELECT
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t.id,
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SELECT t.id,
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t.name,
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t.sex,
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t.head_img,
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addr.tel,
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addr.address,
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a.province
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FROM
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user t
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FROM user t
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LEFT JOIN user_address addr on t.id = addr.user_id
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RIGHT JOIN area a on addr.area_id = a.id
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WHERE (
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@ -92,6 +85,7 @@ WHERE (
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```
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说明:
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* UserDTO.class 查询结果类(resultType)
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* selectAll(UserDO.class) 查询主表全部字段(主表实体类)
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* select() mp的select策略是覆盖,以最后一次为准,这里的策略是追加,可以一直select
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@ -123,19 +117,16 @@ class test {
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对应sql
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```sql
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SELECT
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t.id,
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SELECT t.id,
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t.name,
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t.sex,
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t.head_img,
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addr.tel,
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addr.address,
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a.province
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FROM
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user t
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FROM user t
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LEFT JOIN user_address addr on t.id = addr.user_id
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RIGHT JOIN area a on addr.area_id = a.id
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LIMIT ?,?
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RIGHT JOIN area a on addr.area_id = a.id LIMIT ?,?
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```
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### 还可以这么操作,但不建议
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@ -169,8 +160,7 @@ class test {
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对应sql
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```sql
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SELECT
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t.id,
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SELECT t.id,
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t.name,
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t.sex,
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t.head_img,
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@ -178,8 +168,7 @@ SELECT
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addr.address,
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CASE t.sex WHEN '男' THEN '1' ELSE '0' END AS sex,
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sum(a.province) as province
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FROM
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user t
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FROM user t
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LEFT JOIN (select * from user_address) addr on t.id = addr.user_id
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RIGHT JOIN area a on addr.area_id = a.id
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WHERE (
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@ -201,12 +190,17 @@ class test {
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private UserMapper userMapper;
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void testJoin() {
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List<UserDTO> list = userMapper.selectJoinList(UserDTO.class, new MyLambdaQueryWrapper<UserEntity>()
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.selectAll(UserEntity.class)
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.leftJoin(UserEntity::getId, UserAddressEntity::getUserId,
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r1 -> r1.select(UserAddressEntity::getAddress)
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.leftJoin(UserAddressEntity::getAreaId, AreaEntity::getId,
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r2 -> r2.select(AreaEntity::getProvince))));
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List<UserDTO> list = userMapper.selectJoinList(UserDTO.class,
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new MyLambdaQueryWrapper<UserDO>()
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.selectAll(UserDO.class)
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.select(UserAddressDO::getTel)
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.selectAs(UserAddressDO::getAddress, UserDTO::getUserAddress)
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.select(AreaDO::getProvince, AreaDO::getCity)
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.leftJoin(UserAddressDO.class, UserAddressDO::getUserId, UserDO::getId)
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.leftJoin(AreaDO.class, AreaDO::getId, UserAddressDO::getAreaId)
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.eq(true, UserDO::getId, 1)
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.like(true, UserAddressDO::getTel, "1")
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.gt(true, UserDO::getId, 5));
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}
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}
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```
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@ -214,98 +208,71 @@ class test {
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对应sql
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```sql
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SELECT t0.name,
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t0.sex,
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t0.head_img,
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t0.id,
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t1.address,
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t2.province
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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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LEFT JOIN area t2 ON t1.area_id = t2.id
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```
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sql -> 伪代码
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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(UserDTO.class, new MyLambdaQueryWrapper<user表>()
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.selectAll(user表实体类.class)//查询user表全部字段
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.leftJoin(user表on字段, user_address表on字段,
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user_address表对象 -> user_address表对象
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.select(user_address表address字段)
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.leftJoin(user_address表表的on字段, area表的on字段,
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area表对象 -> area表对象.select(area表的province字段))));
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}
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}
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```
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#### 字段别名,查询字段别名 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(UserDTO.class, 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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}
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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,
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t1.address,
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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
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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(UserDTO.class, 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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}
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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,
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t0.sex,
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t0.head_img,
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t0.id,
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t1.address,
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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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SELECT user.id,
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user.name,
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user.sex,
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user.head_img,
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user_address.tel,
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user_address.address AS userAddress,
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area.province,
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area.city
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FROM user
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LEFT JOIN user_address ON user_address.user_id = user.id
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LEFT JOIN area ON area.id = user_address.area_id
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WHERE (
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t0.id = ?
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AND t1.tel LIKE ?
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AND t0.id = t1.user_id)
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user.id = ?
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AND user_address.tel LIKE ?
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AND user.id > ?)
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```
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说明:
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* UserDTO.class 查询结果返回类(resultType)
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* selectAll() 查询指定实体类的全部字段
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* select() 查询指定的字段,支持可变参数,同意个select只能查询相同表的字段
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故将UserAddressDO和AreaDO分开为连个select
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* selectAs() 字段别名查询,用于数据库字段与业务实体类属性名不一致时使用
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* leftJoin() 参数说明
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第一个参数:参与连表的实体类class
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第二个参数数:连表的ON字段,这个属性必须是第一个参数实体类的属性
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第三个参数:参与连表的另一个实体类属性
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* 条件查询,可以查询主表以及参与连接的所有表的字段,全部调用mp原生的方法,正常使用没有sql注入风险
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#### 分页查询
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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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IPage<UserDTO> iPage = userMapper.selectJoinPage(new Page<>(2, 10), UserDTO.class,
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new MyLambdaQueryWrapper<UserDO>()
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.selectAll(UserDO.class)
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.select(UserAddressDO::getTel)
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.selectAs(UserAddressDO::getAddress, UserDTO::getUserAddress)
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.select(AreaDO::getProvince, AreaDO::getCity)
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.leftJoin(UserAddressDO.class, UserAddressDO::getUserId, UserDO::getId)
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.leftJoin(AreaDO.class, AreaDO::getId, UserAddressDO::getAreaId));
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}
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}
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```
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对应sql
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```mysql
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SELECT user.id,
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user.name,
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user.sex,
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user.head_img,
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user_address.tel,
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user_address.address AS userAddress,
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area.province,
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area.city
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FROM user
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LEFT JOIN user_address ON user_address.user_id = user.id
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LEFT JOIN area ON area.id = user_address.area_id
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LIMIT ?,?
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```
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@ -14,6 +14,7 @@ import org.apache.ibatis.reflection.property.PropertyNamer;
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import java.util.Arrays;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.Objects;
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import static java.util.stream.Collectors.joining;
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@ -93,8 +94,9 @@ public abstract class MyAbstractLambdaWrapper<T, Children extends MyAbstractLamb
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private ColumnCache getColumnCache(String fieldName, Class<?> lambdaClass) {
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ColumnCache columnCache = columnMap.get(LambdaUtils.formatKey(fieldName));
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Assert.notNull(columnCache, "can not find lambda cache for this property [%s] of entity [%s]",
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fieldName, lambdaClass.getName());
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if (Objects.isNull(columnCache)) {
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columnCache = new ColumnCache(fieldName, null);
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}
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return columnCache;
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}
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@ -118,10 +118,20 @@ public class MyLambdaQueryWrapper<T> extends MyAbstractLambdaWrapper<T, MyLambda
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public final <S, X> MyLambdaQueryWrapper<T> selectAs(SFunction<S, ?> columns, SFunction<X, ?> alias) {
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Class<S> clazz = MyLambdaUtils.getEntityClass(columns);
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TableInfo info = TableInfoHelper.getTableInfo(clazz);
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Assert.notNull(info, "table can not be find for lambda");
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selectColumns.add(new SelectColumn(clazz, info.getTableName(), MyLambdaUtils.getColumn(columns), MyLambdaUtils.getName(alias)));
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return typedThis;
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}
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public final MyLambdaQueryWrapper<T> selectAll(Class<?> clazz) {
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TableInfo info = TableInfoHelper.getTableInfo(clazz);
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Assert.notNull(info, "table can not be find -> %s", clazz);
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selectColumns.add(new SelectColumn(clazz, info.getTableName(), info.getKeyColumn(), null));
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info.getFieldList().forEach(c ->
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selectColumns.add(new SelectColumn(clazz, info.getTableName(), c.getColumn(), null)));
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return typedThis;
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}
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@Override
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public String getSqlSelect() {
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if (StringUtils.isBlank(sqlSelect.getStringValue())) {
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