一、方法一:使用注解

1、自定义sql方法

@Repository
public interface UserInfoMapper extends BaseMapper<UserInfo> {
    @Select("select * from user ${ew.customSqlSegment}")
  List<UserInfo> selectAll(@Param(Constants.WRAPPER) Wrapper<UserInfo> wrapper);
}

2、调用自定义sql方法

/**
 * 自定义查询
 */
@Test
public void selectByMy() {
    LambdaQueryWrapper<UserInfo> lambda = new LambdaQueryWrapper<UserInfo>();
    lambda.like(UserInfo::getUsername,"娟")
            .and(lqw->lqw.lt(UserInfo::getAge,40).or().isNotNull(UserInfo::getEmail));
    List<UserInfo> userInfoList = userInfoMapper.selectAll(lambda);
    userInfoList.forEach(System.out::println);
}

二、方法二:使用xml

1、配置路径
mybatis-plus.mapper-locations= com.xiao.permission_system.mapper.UserInfoMapper

2、在xml文件里写sql,去掉UserInfoMapper方法里的注解

<mapper namespace="com.xiao.permission_system.mapper.UserInfoMapper">
  <select id="selectAll" resultMap="com.xiao.permission_system.entity.UserInfo">
    select * from user ${ew.customSqlSegment}
  </select>
</mapper>