hive 查询某个月天数,两个日期相差天数

1、查询某个月天数
select substring(时间,1,4) as 年,substring(时间,6,2) as 月份,
COALESCE(CAST(sum(num1) as double),0) as num1,COALESCE(cast(SUM(NUM2) as double),0) as NUM2 ,
cast((datediff(last_day(substring(时间,1,10)),trunc(substring(时间,1,10),'MM')) + 1) as double) as ts from 表 
group by substring(时间,1,4),substring(时间,6,2),(datediff(last_day(substring(时间,1,10)),trunc(substring(时间,1,10),'MM')) + 1)


2、查询两个日期相差天数
a、datediff(from_unixtime(结束时间,’yyyy-MM-dd HH:mm:ss’), 开始时间)；
b、datediff(结束时间, 开始时间)。