1、獲取年份

    select YEAR(CURDATE());
    2018

2、獲取月份

select MONTH(CURDATE());
12

3、獲取日期

select DATE(CURDATE());
14

4、獲取當年一月份

select CONCAT(YEAR(CURDATE()),'-','01');
2018-01

總結：
其實前3個函式的用法就是MONTH(時間)，例如：

select MONTH('2018-05-08')
5

例如：

select avg(flow) flow,avg(talk) talk,avg
 
(cost) cost from bill where 
MONTH(CURDATE()) - MONTH(b_time) < 5 
and uid = (select uid from user where phone = 13277924031)