摘采自牛客网：https://blog.nowcoder.net/n/41cb34b72c5545cd8b39adb58314b7fd?f=comment

题目：描述

Orders订单表

【问题】编写 SQL 语句，返回 2020 年 1 月的所有订单的订单号（order_num）和订单日期（order_date），并按订单日期升序排序

【示例结果】

返回订单号order_num，和order_date订单时间

【示例解析】

a0001、a0002、a0003 时间属于2020年1月

一题多解法：

字符串匹配（近似查找法）

用like来查找

select order_num, order_date

from Orders

where order_date like '2020-01%'

order by order_date

切割字符串

select order_num, order_date

from Orders

where left(order_date, 7) = '2020-01'

order by order_date

字符串比较

select *

from Orders

where order_date >= '2020-01-01 00:00:00' and order_date <= '2020-01-31 23:59:59'

order by order_date;

用正则来查找（效率不如like，能用like就用like）

select order_num, order_date

from Orders

where order_date regexp '2020-01'

order by order_date

时间函数匹配

select order_num, order_date

from Orders

where year(order_date) = '2020' and month(order_date) = '1'

order by order_date

利用date_format函数 （参考其中的匹配规则进行匹配）

select order_num, order_date

from Orders

where date_format(order_date, '%Y-%m')='2020-01'

order by order_date