查询投影

@SpringBootTest
class MybatisplusApplicationTests {
    @Autowired
    private UserDao userDao;

    @Test
    void testGetAll() {

        // 查询投影
        LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<user>();
        lqw.select(User::getId, User::getName, User::getAge);

        QueryWrapper<User> lqw = new QueryWrapper<User>();
        lqw.select("id", "name", "age", "tel")

        QueryWrapper<User> lqw = new QueryWrapper<User>();
        // lqw.select("count(*)")
        lqw.select("count(*) as count")

        lqw.groupBy("tel")
        List<Map<String, Object>> userList = userDao.selectMaps(lqw);
        System.out.println(userList);

    }
}