1，前提
今天看同事写的sql里面出现了时间类的函数，平时自己也经常用到，每次都要百度，还不如自己整理记录在一起，方便后续使用。
2，sql时间函数
2.1 获取当前时间：
selectNOW() as '当前日期+时间',CURDATE() as '当前日期',CURTIME() as '当前时间';
2.2 获取单个年月日时分秒
SELECT YEAR(now() ) AS '年',MONTH(now()) AS '月',DAY(now()) AS '日',HOUR(now()) AS '时',MINUTE(now()) AS '分',SECOND(now()) AS '秒',DAYNAME(now()) AS '星期';
2.3 格式化日期
SELECTNOW() AS "当前时间",DATE_FORMAT(NOW(), '%Y.%m.%d') AS '格式化日期',DATE_FORMAT(NOW(), '%Y/%m/%d') AS '格式化日期',DATE_FORMAT(NOW(), '%Y-%m-%d') AS '格式化日期',TIME_FORMAT(NOW(), '%H:%i:%s') AS '格式化时间';
2.4 计算日期
selectNOW() as "现在时间",DATE_ADD(NOW(), interval 1 year) as "增加1年",DATE_ADD(NOW(), interval 1 month) as "增加1个月",DATE_ADD(NOW(), interval 1 day) as "增加1天",DATE_ADD(NOW(), interval 1 hour) as "增加1小时",DATE_SUB(NOW(), interval 1 year) as "减少1年",DATE_SUB(NOW(), interval 1 month) as "减少1个月",DATE_SUB(NOW(), interval 1 day) as "减少1天",DATE_SUB(NOW(), interval 1 hour) as "减少1小时";
selectNOW() as "现在时间",DATE_ADD(NOW(), interval 1 year) as "增加1年",DATEDIFF(NOW(), DATE_ADD(NOW(), interval 1 year)) as "间隔天数";
好文推荐：
https://zhuanlan.zhihu.com/p/533691995
