MyBatisPlus-聚合查询、分组查询及等值查询

@SpringBootTest 
class Mybatisplus02DqlApplicationTests { 
    @Autowired 
    private UserDao userDao; 
    @Test 
    void testGetAll(){ 
        QueryWrapper<User> lqw = new QueryWrapper<User>(); 
        //lqw.select("count(*) as count"); 
        //SELECT count(*) as count FROM user 
        //lqw.select("max(age) as maxAge"); 
        //SELECT max(age) as maxAge FROM user 
        //lqw.select("min(age) as minAge");
        //SELECT min(age) as minAge FROM user 
        //lqw.select("sum(age) as sumAge"); 
        //SELECT sum(age) as sumAge FROM user 
        lqw.select("avg(age) as avgAge"); 
        //SELECT avg(age) as avgAge FROM user 
        List<Map<String, Object>> userList = userDao.selectMaps(lqw); 
        System.out.println(userList); 
    } 
}

@SpringBootTest 
class Mybatisplus02DqlApplicationTests { 
    @Autowired 
    private UserDao userDao; 
    @Test 
    void testGetAll(){ 
        QueryWrapper<User> lqw = new QueryWrapper<User>(); 
        lqw.select("count(*) as count,tel"); 
        lqw.groupBy("tel"); 
        List<Map<String, Object>> list = userDao.selectMaps(lqw); 
        System.out.println(list); 
    }
}

SELECT count(*) as count,tel FROM user GROUP BY tel

@SpringBootTest 
class Mybatisplus02DqlApplicationTests { 
    @Autowired 
    private UserDao userDao; 
    @Test 
    void testGetAll(){ 
        LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>(); 
        lqw.eq(User::getName, "Jerry").eq(User::getPassword, "jerry"); 
        User loginUser = userDao.selectOne(lqw); 
        System.out.println(loginUser); 
    } 
}

SELECT id,name,password,age,tel FROM user WHERE (name = ? AND password = ?)