Hive的常用函数操作

//函数

...................................

//size()提取数据大小
$hive>select size(arr) from emp ;

//是否包含指定元素
$hive>select array_contains(arr,"xx") from emp ;

//查看所有函数
show functions ;

//
desc formatted function array_contains ;
select current_database() ;
select current_user() ;
select current_date() ;

//case when == switch case
SELECT CASE WHEN length(name) <= 4 THEN 'Short' ELSE 'Long' END as xx FROM emp ;

//倒序字符串
select reverse("12345")  ;
SELECT reverse(split(reverse('/home/user/employee.txt'),'/')[0])

//创建数组对象
select array(1,1,1,2,3,4) ;

//collect_set()聚合函数，对结果集进行聚合，返回一个集合。
SELECT collect_set(work_place[0]) AS flat_workplace0 FROM employee;

//虚列，内置列
select INPUT__FILE__NAME from emp ;