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README.md
119
README.md
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* 对 <a href="https://gitee.com/baomidou/mybatis-plus" target="_blank">mybatis-plus</a> 多表查询的扩展
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* <a href="https://gitee.com/best_handsome/mybatis-plus-join-demo" target="_blank">演示工程</a>
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* <a href="https://www.baidu.com/link?url=cknmzNRg3E2p9d0BbUuQ2MBYCSSs6u1LCtNm5RzIzui&wd=&eqid=a5bbe908000085540000000563f830c5" target="_blank">文档</a>
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* <a href="https://www.baidu.com/link?url=cknmzNRg3E2p9d0BbUuQ2MBYCSSs6u1LCtNm5RzIzui&wd=&eqid=a5bbe908000085540000000563f830c5" target="_blank">插件文档 https://ylctmh.com</a>
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* 点个Star支持一下吧 :)
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QQ群:1022221898
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<a href="https://gitee.com/best_handsome/mybatis-plus-join/issues/I65N2M" target="_blank">加入微信群</a>
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<a href="https://gitee.com/best_handsome/mybatis-plus-join/issues/I65N2M" target="_blank">添加作者微信，备注MPJ，加入微信群</a>
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<img width="200px" src="https://ylctmh.com/qr.png" alt="添加作者微信，备注MPJ，加入微信群"/>
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### <a href="https://www.baidu.com/link?url=cknmzNRg3E2p9d0BbUuQ2MBYCSSs6u1LCtNm5RzIzui&wd=&eqid=a5bbe908000085540000000563f830c5" target="_blank">文档</a>
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### <a href="https://www.baidu.com/link?url=cknmzNRg3E2p9d0BbUuQ2MBYCSSs6u1LCtNm5RzIzui&wd=&eqid=a5bbe908000085540000000563f830c5" target="_blank">插件文档 https://ylctmh.com</a>
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## 使用方法
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@ -48,7 +49,7 @@ class test {
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void testJoin() {
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//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
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MPJLambdaWrapper<UserDO> wrapper = new MPJLambdaWrapper<UserDO>()
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MPJLambdaWrapper<UserDO> wrapper = JoinWrappers.lambda(User.class)
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.selectAll(UserDO.class)//查询user表全部字段
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.select(UserAddressDO::getTel)//查询user_address tel 字段
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.selectAs(UserAddressDO::getAddress, UserDTO::getUserAddress)//别名
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@ -147,113 +148,5 @@ MPJLambdaWrapper其他功能
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* <a href="https://ylctmh.com/pages/core/lambda/select/selectFunc.html" target="_blank">简单的SQL函数使用</a>
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* <a href="https://ylctmh.com/pages/core/lambda/join/leftJoin.html" target="_blank">ON语句多条件支持</a>
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### String形式用法（MPJQueryWrapper）
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#### 简单的连表查询
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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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MPJQueryWrapper wrapper = new MPJQueryWrapper<UserDO>()
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.selectAll(UserDO.class)
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.select("addr.tel", "addr.address", "a.province")
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.leftJoin("user_address addr on t.id = addr.user_id")
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.rightJoin("area a on addr.area_id = a.id")
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.like("addr.tel", "1")
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.le("a.province", "1");
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//列表查询
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List<UserDTO> list = userMapper.selectJoinList(UserDTO.class, wrapper);
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//分页查询 （需要启用 mybatis plus 分页插件）
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Page<UserDTO> listPage = userMapper.selectJoinPage(new Page<>(1, 10), UserDTO.class, wrapper);
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}
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}
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```
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对应sql
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```
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SELECT
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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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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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addr.tel LIKE ?
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AND a.province <= ?)
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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)默认主表别名 "t"
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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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主表字段可以用lambda,会自动添加表别名,主表别名默认是 t ,非主表字段必须带别名查询
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* leftJoin() rightJoin() innerJoin() 传sql片段 格式 (表 + 别名 + 关联条件)
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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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#### 还可以这么操作,但不建议
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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,
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new MPJQueryWrapper<UserDO>()
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.selectAll(UserDO.class)
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.select("addr.tel", "addr.address")
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//行列转换
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.select("CASE t.sex WHEN '男' THEN '1' ELSE '0' END AS sex")
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//求和函数
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.select("sum(a.province) AS province")
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//自定义数据集
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.leftJoin("(select * from user_address) addr on t.id = addr.user_id")
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.rightJoin("area a on addr.area_id = a.id")
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.like("addr.tel", "1")
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.le("a.province", "1")
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.orderByDesc("addr.id"));
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}
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}
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```
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对应sql
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```
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SELECT
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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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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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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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addr.tel LIKE ?
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AND a.province <= ?)
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ORDER BY
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addr.id DESC
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```
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# <a href="https://www.baidu.com/link?url=cknmzNRg3E2p9d0BbUuQ2MBYCSSs6u1LCtNm5RzIzui&wd=&eqid=a5bbe908000085540000000563f830c5" target="_blank">wiki</a>
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# <a href="https://www.baidu.com/link?url=cknmzNRg3E2p9d0BbUuQ2MBYCSSs6u1LCtNm5RzIzui&wd=&eqid=a5bbe908000085540000000563f830c5" target="_blank">插件文档 wiki https://ylctmh.com</a>
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@ -54,6 +54,11 @@ public class MPJLambdaQueryWrapper<T> extends AbstractLambdaWrapper<T, MPJLambda
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*/
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private List<String> ignoreColumns = new ArrayList<>();
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/**
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* 是否 select distinct
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*/
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private boolean selectDistinct = false;
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/**
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* 不建议直接 new 该实例，使用 Wrappers.lambdaQuery(entity)
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*/
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@ -209,6 +214,15 @@ public class MPJLambdaQueryWrapper<T> extends AbstractLambdaWrapper<T, MPJLambda
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return sqlSelect.getStringValue();
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}
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/**
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* sql去重
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* select distinct
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*/
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public MPJLambdaQueryWrapper<T> distinct() {
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this.selectDistinct = true;
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return typedThis;
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}
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public String getFrom() {
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return from.getStringValue();
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}
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@ -218,6 +232,10 @@ public class MPJLambdaQueryWrapper<T> extends AbstractLambdaWrapper<T, MPJLambda
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return alias;
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}
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public boolean getSelectDistinct() {
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return selectDistinct;
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}
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/**
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* 用于生成嵌套 sql
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* <p>故 sqlSelect selectColumn ignoreColumns from不向下传递</p>
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