Mybatis-Plus中的查询指定字段

select word from addition;

public void test3(){
    LambdaQueryWrapper<Addition> queryWrapper = new LambdaQueryWrapper<>();
    queryWrapper.select(Addition::getWord);
     //方法一:通过stream流操作
    List<String> list = additonService.list(queryWrapper).stream().map(Addition::getWord).collect(Collectors.toList());
    //方式二:listObjs
    List<Object> list1 = additionService.listObjs(queryWrapper);
}

select * from addition;

select word from addition;

public void selectByWrapper1() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.select("name", "phone").eq("age",25);
        List<User> users = userMapper.selectList(queryWrapper);
        users.forEach(System.out::println);
    }

public void selectByWrapper2() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.select(User.class, info -> !info.getColumn().equals("age")
                && !info.getColumn().equals("address")).eq("name","jack");
        List<User> users = userMapper.selectList(queryWrapper);
        users.forEach(System.out::println);
    }

public void selectMaps2(){
        QueryWrapper<User> userQueryWrapper = Wrappers.query();

        userQueryWrapper.select("avg(age) avg_age" , "min(age) min_age" , "max(age) max_age")
                        .groupBy("age")
                        .having("sum(age) < {0}" , 60);
        List<Map<String , Object>> mapList = userMapper.selectMaps(userQueryWrapper);
        mapList.forEach(System.out::println);
    }