hive之substr函数

select 
case 
when int(substr(time,1,2))<05 then 1
when int(substr(time,1,2))>=05 and int(substr(time,1,2))<12 then 2
when int(substr(time,1,2))>=12 and int(substr(time,1,2))<18 then 3
when int(substr(time,1,2))>=18 then 4 end apply_period

substr(time,1,8) 表示将time从第1位开始截取，截取的长度为8位，hive的第一个下标是1不是0。

这里感谢xiangzong.