HIVE中的几种排序

1、order by：全局排序
　　select * from emp order by sal;

2、sort by：对于每个reduce进行排序
　　set mapreduce.job.reduces=3;

　　

　　insert overwrite local directory '/opt/datas/emp_sort'  row format delimited fields terminated by '\t' select * from emp sort by sal;

　　

　　结果：

　　

3、distribute by :底层就是mapreduce 的分区，一般与sort by连用
　　insert overwrite local directory '/opt/datas/emp_dis' row format delimited fields terminated by '\t' select * from emp distribute by deptno sort by sal;

　　

4、cluster by:等价于distribute by 与sort by的字段相同时

　　insert overwrite local directory '/opt/datas/emp_cls'  row format delimited fields terminated by '\t'  select * from emp cluster by sal;