1.datediff()
datediff(startdate,enddate)
返回两个日期相差的天数
2.date_add()
#对于某个日期加上n分钟n秒
#对于某个日期加上n小时n分钟n秒
#对于日期加上几天几小时几分钟几秒钟
3.lag()和lead()
lag(字段名称 , 向上偏移量 , 超出范围时默认值) over (partion by …order by …)
lead(字段名称 , 向下偏移量 , 超出范围时默认值) over (partion by …order by …)
例题：leetcode 197题
#方法一
-- select id
-- from
-- (
-- select id,recordDate,Temperature,lag(recordDate,1,Null) over (order by recordDate) yd,
-- lag(Temperature,1,100) over (order by recordDate) yt
-- from Weather
-- ) a
-- where datediff(a.recordDate,a.yd)=1
-- and a.Temperature>a.yt;
#方法二
-- select a.id
-- from Weather a
-- inner join Weather b
-- on datediff(a.recordDate,b.recordDate)=1
-- and a.Temperature>b.Temperature;
#方法三
select a.id
from weather a
inner join weather b
on (a.recorddate = adddate(b.recorddate,INTERVAL 1 day))
where a.temperature > b.temperature;
datediff()、adddate()、lag()、lead()
原文：https://www.cnblogs.com/hugrice/p/14696366.html