mybatis plus 不持支case when

MyBatis Plus是一个基于MyBatis的增强工具，它提供了很多便捷的功能来简化开发过程。然而，目前的版本（3.4.0及以下）不直接支持在查询条件中使用case when语句。

如果你需要在查询条件中使用case when语句，可以通过自定义SQL来实现。你可以使用MyBatis Plus提供的@Select注解或者XML配置文件来编写自定义SQL语句，然后在代码中调用相应的方法执行查询操作。

以下是一个示例，展示了如何使用自定义SQL来实现case when语句：

1. 在Mapper接口中定义自定义SQL方法：

@Select("SELECT * FROM your_table WHERE CASE WHEN condition1 THEN column1 WHEN condition2 THEN column2 ELSE column3 END = #{value}")
List<YourEntity> selectByCaseWhen(@Param("value") String value);

2. 在代码中调用自定义SQL方法：

List<YourEntity> result = yourMapper.selectByCaseWhen("some_value");

请注意，以上示例中的"your_table"和"your_entity"需要替换为你实际的表名和实体类名。

相关问题

mybatis-plus set

MyBatis-Plus is a popular persistence framework for Java applications, which provides additional features and enhancements to the original MyBatis framework. When it comes to the "set" operation in MyBatis-Plus, it typically refers to updating records in a database table.

In MyBatis-Plus, you can use the `UpdateWrapper` or `LambdaUpdateWrapper` class to build update operations with the "set" clause. Here is an example of how to use the "set" operation in MyBatis-Plus:

UpdateWrapper<User> updateWrapper = new UpdateWrapper<>();
updateWrapper.set("name", "John")
            .set("age", 25)
            .eq("id", 1);

int affectedRows = userMapper.update(null, updateWrapper);

In this example, we create an `UpdateWrapper` instance and use the `set` method to specify the columns and their new values that we want to update. We then use other methods like `eq` to add conditions for the update operation, in this case, updating records with the ID equal to 1.

Finally, we call the `update` method on the mapper interface, passing `null` as the entity parameter because we are only updating specific columns without modifying other fields. The `update` method returns the number of affected rows.

This is just a basic example, and there are more advanced features available in MyBatis-Plus for complex update operations. You can refer to the official documentation or explore more examples to learn about other functionalities provided by MyBatis-Plus.

springboot+mybatis-plus配置yml文件

以下是在SpringBoot中使用MyBatis-Plus的示例yaml配置文件：

server:
  port: 8080

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/mybatis_plus_demo?useUnicode=true&characterEncoding=utf8&serverTimezone=Asia/Shanghai
    username: root
    password: my_mysql_password
  # 配置Mybatis-Plus
  mybatis-plus:
    # 开启驼峰命名法自动映射
    configuration:
      map-underscore-to-camel-case: true
    # 实体扫描，多个package用逗号或分号分隔
    typeAliasesPackage: com.example.demo.entity
    # SQL语句打印输出，开发阶段建议开启
    # 可以通过 mybatis-plus.global-config.sql-mapper-xml=true 关闭默认XML映射配置
    global-config:
      db-config:
        # 逻辑已删除字段自动填充值
        logic-delete-value: 1
        logic-not-delete-value: 0
      sql-injector: com.baomidou.mybatisplus.core.injector.LogicSqlInjector
      sql-parser: com.baomidou.mybatisplus.extension.parsers.BlockAttackSqlParser
      sql-explain: true
  # 配置自动刷新，修改xml后不用重新启动项目
  # ctrl + shift + A 输入 Registry，勾选Registry...，在Registry中 搜索compile.automake.allow.when.app.running，将其勾选上
  devtools:
    restart:
      enabled: true
      # 需要自动扫描的文件后缀名
      additional-paths: src/main/java

在上述配置文件中，我们配置了数据库连接信息和MyBatis-Plus的各种选项，以及DevTools的配置，以便我们修改代码后可以自动重新加载。