每天学习笔记系列-HIVE SQL : ORDER BY 与 SORT BY

之前一直没太关注 order by 和sort by的区别，今天看了下。

 

首先 ，如果在 严格模式下直接使用order by 会报错，必须加上 LIMIT关键字;

 In strict mode, if ORDER BY is specified, LIMIT must also be specified.

set hive.mapred.mode=nonstrict;  #或者将参数值设置为，nostrict
select 
*
from 
A
where d ='2018-10-22'
order by checkin_time 
limit 100

sort  by 的语法不会受到set hive.mapred.mode 参数影响，
 

select 
*
from 
A
where d ='2018-10-22' 
sort by checkin_time 

 

 distribute  by  $   按指定的key 去分发数据，相同key数据会被分到同一个reduce

select 
*
from 
A
where d ='2018-10-22'
distribute by clientname  
sort by checkin_time 


#cluster by 等价于以上语句，但是cluster by 只能降序


select 
*
from 
A
where d ='2018-10-22' 
cluster by checkin_time