Hive常用函数及自定义函数

前言:
    HQL常用函数语法和RDBMS语法相似
    官网参考:
    https://cwiki.apache.org/confluence/display/Hive/LanguageManual+Select
    https://cwiki.apache.org/confluence/display/Hive/LanguageManual+UDF

一.Hive自带函数

 -- 查看系统自带函数 hive> show functions;
 least
 length
 like
 max
 min
 -- 查看函数使用帮助

 
hive
> desc function extended upper;
 Example:
  > SELECT upper('Facebook') FROM src LIMIT 1;
  'FACEBOOK'

二.常用的函数语法
 举例:

 hive> select * from emp;
 OK
 7369 SMITH CLERK 7902 1980-12-17 800.0 NULL 20
 7499 ALLEN SALESMAN 7698 1981-2-20 1600.0 300.0 30
 7521 WARD SALESMAN 7698 1981-2-22 1250.0 500.0 30
 7566 JONES MANAGER 7839 1981-4-2 2975.0 NULL 20
 7654 MARTIN SALESMAN 7698 1981-9-28 1250.0 1400.0 30
 7698 BLAKE MANAGER 7839 1981-5-1 2850.0 NULL 30
 7782 CLARK MANAGER 7839 1981-6-9 2450.0 NULL 10
 7788 SCOTT ANALYST 7566 1987-4-19 3000.0 NULL 20
 7839 KING PRESIDENT NULL 1981-11-17 5000.0 NULL 10
 7844 TURNER SALESMAN 7698 1981-9-8 1500.0 0.0 30
 7876 ADAMS CLERK 7788 1987-5-23 1100.0 NULL 20
 7900 JAMES CLERK 7698 1981-12-3 950.0 NULL 30
 7902 FORD ANALYST 7566 1981-12-3 3000.0 NULL 20
 7934 MILLER CLERK 7782 1982-1-23 1300.0 NULL 10
 8888 HIVE PROGRAM 7839 1988-1-23 10300.0 NULL NULL

 -- 根据工资降序排序 取前三
 hive> select * from emp order by salary desc limit 3;
 OK
 7369 SMITH CLERK 7902 1980-12-17 800.0 NULL 20
 7900 JAMES CLERK 7698 1981-12-3 950.0 NULL 30
 7876 ADAMS CLERK 7788 1987-5-23 1100.0 NULL 20

 -- 求每个部门的最大工资,最小工资,平均工资,所有工资
 select deptno, max(salary),min(salary),avg(salary),sum(salary) from ruozedata_emp group by deptno
 OK NULL    10300.0 10300.0 10300.0 10300.0 10      5000.0  1300.0  2916.6666666666665      8750.0 20      3000.0  800.0   2175.0  10875.0 30      2850.0  950.0   1566.6666666666667      9400.0

 -- 求每个部门的最大工资,最小工资,平均工资,所有工资中平均工资大于2000
 select deptno, max(salary),min(salary),avg(salary),sum(salary) from ruozedata_emp group by deptno
 where avg(salary)>3000
 OK
 NULL 10300.0 10300.0 10300.0 10300.0
 20 3000.0 800.0 2175.0 10875.0

 -- 求每个部门工资前2的姓名和工资
 select t.*
 from
 (select
 deptno,
 ename,
 salary,
 row_number() over(partition by deptno order by salary desc ) as number
 from emp)t
 where t.number<=2;
 OK
 NULL HIVE 10300.0 1
 10 KING 5000.0 1
 10 CLARK 2450.0 2
 20 SCOTT 3000.0 1
 20 FORD 3000.0 2
 30 BLAKE 2850.0 1
 30 ALLEN 1600.0 2

 -- 统计每个部门的人数
 select deptno,count(1) from emp group by deptno;
 OK
 NULL 1
 10 3
 20 5
 30 6

 -- CASE WHEN统计工资情况
 select ename,salary,
 case
 when salary>1 and salary<=1000 then 'lower'
 when salary>1000 and salary<=2000 then 'middle'
 when salary>2000 and salary<=4000 then 'high'
 else 'highest'
 end
 from emp

OK
SMITH   800.0   lower
ALLEN   1600.0  middle
WARD    1250.0  middle
JONES   2975.0  high
MARTIN  1250.0  middle
BLAKE   2850.0  high

 -- 类型转换
 hive> select cast('2018-06-17' as date) from dual; OK 2018-06-17

 -- 截取字符串
 hive> select substr('abcdef',1,5) from dual; OK abcde

 -- 拼接
 hive> select concat('123','456') from dual; OK 123456
 -- 制定分割拼接
 hive> select concat_ws('.','www','baidu','com') from dual; OK www.baidu.com

 -- 获取长度
 hive> select length(concat_ws('.','www','baidu','com')) from dual; OK
 -- split拆分
 hive> select split(concat_ws('.','www','baidu','com'),'\\.') from dual; OK ["www","baidu","com"] Time taken: 0.084 seconds, Fetched: 1 row(s)

 -- 拆分换行

 hive> select explode(split(concat_ws('.','www','baidu','com'),'\\.') ) from dual;
 OK
 www
 baidu
 com

 -- 大写转换小写 hive> select lower('ABC') from dual; OK abc

 -- 小写转换大写 hive> select upper('abc') from dual; OK ABC

 -- json导入查询
 hive> create table json(json string);
 OK
 Time taken: 0.059 seconds
 -- 加载json文件
 hive> load data local  inpath'/home/hadoop/data/test.json' into table json;
 hive> select * from json;
 OK
 {"name":"zhangsan","age":28,"addr":"hz"}
 {"name":"lisi","age":18,"addr":"bj"}
 {"name":"wangwu","age":10,"addr":"sh"}
 Time taken: 0.151 seconds, Fetched: 3 row(s)
 -- json_tuple查询
 hive> select json_tuple(json,'name','age','addr') as (name,age,addr)  from json; OK zhangsan        28      hz lisi            18      bj wangwu          10      sh Time taken: 0.077 seconds, Fetched: 3 row(s)

三.常用时间函数

 -- current_date返回年 月 日

hive> select current_date  from dual;
OK
2018-06-07

--  返回unix时间搓
hive> select unix_timestamp() from dual;
OK
1528403209

--  current_timestamp返回年月入时分秒
hive> select current_timestamp from dual;
OK
2018-06-07 16:35:12.752
Time taken: 0.217 seconds, Fetched: 1 row(s)

-- 获取年月日
hive> select to_date('2018-06-07 16:44:44') from dual;
OK
2018-06-07

-- 获取年
hive> select year('2018-06-07 16:44:44') from dual;
OK
2018

-- 获取月
hive> select month('2018-06-07 16:44:44') from dual;
OK
6

-- 获取日
hive> select day('2018-06-07 16:44:44') from dual;
OK
7

-- 获取小时
hive> select hour('2018-06-07 16:44:44') from dual;
OK
16

-- 获取分钟
hive> select minute('2018-06-07 16:44:44') from dual;
OK
44

-- 获取秒
hive> select second('2018-06-07 16:44:44') from dual;
OK

-- 时间天相加
hive> select date_add('2018-06-07',10) from dual;
OK
2018-06-17

-- 时间天相减
hive> select date_sub('2018-06-17',10) from dual;
OK
2018-06-07

四.自定义函数

.....

    

来自 “ ITPUB博客 ” ，链接：http://blog.itpub.net/31441024/viewspace-2155864/，如需转载，请注明出处，否则将追究法律责任。

转载于:http://blog.itpub.net/31441024/viewspace-2155864/