hive 常用函数整理 7.字符串函数

1. 字符串长度函数：length

语法: length(string A)

返回值: int

说明：返回字符串A的长度

举例：

hive> select length('abcedfg') from student;

7

hive> select length(null) from student;

NULL

2. 字符串反转函数：reverse

语法: reverse(string A)

返回值: string

说明：返回字符串A的反转结果

举例：

hive> select reverse('abcedfg') from student;

gfdecba

hive> select reverse('12345') from student;

54321

3. 字符串连接函数：concat

语法: concat(string A, string B…)

返回值: string

说明：返回输入字符串连接后的结果，支持任意个输入字符串

举例：

hive> select concat('a','b','c') from student;

abc

4. 带分隔符字符串连接函数：concat_ws

语法: concat_ws(string SEP, string A, string B…)

返回值: string

说明：返回输入字符串连接后的结果，SEP表示各个字符串间的分隔符

举例：

hive> select concat_ws(',','abc','def','gh') from student;

abc,def,gh

hive> select concat_ws('-','abc','def','gh') from student;

abc-def-gh

5. 字符串截取函数：substr,substring

语法: substr(string A, int start),substring(string A, int start)

返回值: string

说明：返回字符串A从start位置到结尾的字符串

举例：

--从第三个字符截到最后

hive> select substr('abcde',3) from student;

cde

--从第零个字符截到最后

hive> select substr('abcde',0) from student;

abcde

--从第零个字符开始截两个字符

hive> select substr('abcde',0,2) from student;

ab

hive> select substr('abcde',-1) from student; （和ORACLE相同）

e

hive> select substr('abcde',-2) from student;（和ORACLE相同）

de

6. 字符串截取函数：substr,substring

语法: substr(string A, int start, int len),substring(string A, int start, int len)

返回值: string

说明：返回字符串A从start位置开始，长度为len的字符串

举例：

--从第二个字符开始截三个字符

hive> select substr('abcde',2,3) from student;

bcd

hive> select substr('abcde',3,2) from student;

cd

hive> select substring('abcde',3,2) from student;

cd

hive>select substring('abcde',-2,2) from student;

de

7. 字符串转大写函数：upper,ucase

语法: upper(string A) ucase(string A)

返回值: string

说明：返回字符串A的大写格式

举例：

hive> select upper('abSEd') from student;

ABSED

hive> select ucase('abSEd') from student;

ABSED

8. 字符串转小写函数：lower,lcase

语法: lower(string A) lcase(string A)

返回值: string

说明：返回字符串A的小写格式

举例：

hive> select lower('abSEd') from student;

absed

hive> select lcase('abSEd') from student;

absed

9. 去空格函数：trim

语法: trim(string A)

返回值: string

说明：去除字符串两边的空格

举例：

hive> select trim(' abc ') from student;

abc

hive>  select trim('  a b c  ') from student;

a b c

10. 左边去空格函数：ltrim

语法: ltrim(string A)

返回值: string

说明：去除字符串左边的空格

举例：

hive>  select ltrim('  a b c  ') from student;

a b c

11. 右边去空格函数：rtrim

语法: rtrim(string A)

返回值: string

说明：去除字符串右边的空格

举例：

hive>  select rtrim('  a b c  ') from student;

a b c

12. 正则表达式替换函数：regexp_replace

语法: regexp_replace(string A, string B, string C)

返回值: string

说明：将字符串A中的符合java正则表达式B的部分替换为C。注意，在有些情况下要使用转义字符,类似oracle中的regexp_replace函数。

举例：

hive> select regexp_replace('foobar', 'oo|ar', '') from student;

fb

hive> select regexp_replace('123456', '.', '_') from student;

______

hive> select regexp_replace('123456', '1|3|5', '_') from student;

_2_4_6

13. 正则表达式解析函数：regexp_extract

语法: regexp_extract(string subject, string pattern, int index)

返回值: string

说明：将字符串subject按照pattern正则表达式的规则拆分，返回index指定的字符。

举例：

hive> select regexp_extract('foothebar', 'foo(.*?)(bar)', 1) from student;

the

hive> select regexp_extract('foothebar', 'foo(.*?)(bar)', 2) from student;

bar

hive> select regexp_extract('foothebar', 'foo(.*?)(bar)', 0) from student;

Foothebar

hive> select regexp_extract('4.2.3.','\\d.+',0) from student;

4.2.3.

hive> select regexp_extract('4.2.3.','\\d',0) from student;

4

hive> select regexp_extract('4.2.3.','\\d+',0) from student;

4

hive> select regexp_extract('4.2.3.','\\d.\\d.\\d',0) from student;

4.2.3

hive> select regexp_extract('4.2.3.','.\\d.',0) from student;

.2.

--注意，在有些情况下要使用转义字符，下面的等号要用双竖线转义，这是java正则表达式的规则。

select data_field,

regexp_extract(data_field,'.*?bgStart\\=([^&]+)',1) as aaa,

regexp_extract(data_field,'.*?contentLoaded_headStart\\=([^&]+)',1) as bbb,

regexp_extract(data_field,'.*?AppLoad2Req\\=([^&]+)',1) as ccc

from pt_nginx_loginlog_st

where pt = '2012-03-26' limit 2;

14. URL解析函数：parse_url

语法: parse_url(string urlString, string partToExtract [, string keyToExtract])

返回值: string

说明：返回URL中指定的部分。 的有效值为：HOST, PATH, QUERY, REF, PROTOCOL, AUTHORITY, FILE, and USERINFO.

举例：

hive> select parse_url('https://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1', 'HOST') from student;

facebook.com

hive> select parse_url('https://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1', 'QUERY', 'k1') from student;

v1

hive> select parse_url('https://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1', 'PATH') from student;

/path1/p.php

hive> select parse_url('https://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1', 'QUERY') from student;

k1=v1&k2=v2

hive> select parse_url('https://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1', 'REF') from student;

Ref1

hive> select parse_url('https://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1', 'PROTOCOL') from student;

http

hive> select parse_url('https://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1', 'AUTHORITY') from student;

facebook.com

hive> select parse_url('https://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1', 'FILE') from student;

/path1/p.php?k1=v1&k2=v2

hive> select parse_url('https://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1', 'USERINFO') from student;

NULL

15. json解析函数：get_json_object

语法: get_json_object(string json_string, string path)

返回值: string

说明：解析json的字符串json_string,返回path指定的内容。如果输入的json字符串无效，那么返回NULL。

举例：

{

"store": {

"fruit": \[

{

"weight": 8,

"type": "apple"

},

{

"weight": 9,

"type": "pear"

}

],

"bicycle": {

"price": 19.95,

"color": "red"

}

},

"email": "amy@only_for_json_udf_test.net",

"owner": "amy"

}

--获取最顶层的标签

hive>  select  get_json_object('{"store":{"fruit":\[{"weight":8,"type":"apple"},{"weight":9,"type":"pear"}],"bicycle":{"price":19.95,"color":"red"}},"email":"amy@only_for_json_udf_test.net", "owner":"amy"}','$.owner') from student;

Amy

--获取最顶层的标签

hive>  select  get_json_object('{"store":{"fruit":\[{"weight":8,"type":"apple"},{"weight":9,"type":"pear"}],"bicycle":{"price":19.95,"color":"red"}},"email":"amy@only_for_json_udf_test.net", "owner":"amy"}','$.store') from student;

{"fruit":[{"weight":8,"type":"apple"},{"weight":9,"type":"pear"}],"bicycle":{"price":19.95,"color":"red"}}

--获得二层标签

hive> select  get_json_object('{"store":{"fruit":\[{"weight":8,"type":"apple"},{"weight":9,"type":"pear"}],"bicycle":{"price":19.95,"color":"red"}},"email":"amy@only_for_json_udf_test.net", "owner":"amy"}','$.store.fruit') from student;

[{"weight":8,"type":"apple"},{"weight":9,"type":"pear"}]

--获得三层标签

hive> select  get_json_object('{"store":{"fruit":\[{"weight":8,"type":"apple"},{"weight":9,"type":"pear"}],"bicycle":{"price":19.95,"color":"red"}},"email":"amy@only_for_json_udf_test.net", "owner":"amy"}','$.store.fruit.type') from student;

["apple","pear"]

--跨层获取标签（不通过一层获取二层）

hive> select  get_json_object('{"store":{"fruit":\[{"weight":8,"type":"apple"},{"weight":9,"type":"pear"}],"bicycle":{"price":19.95,"color":"red"}},"email":"amy@only_for_json_udf_test.net", "owner":"amy"}','$.bicyle.price') from student;

NULL

--获取最底层标签

hive> select  get_json_object('{"store":{"fruit":\[{"weight":8,"type":"apple"},{"weight":9,"type":"pear"}],"bicycle":{"price":19.95,"color":"red"}},"email":"amy@only_for_json_udf_test.net", "owner":"amy"}','$.store.bicycle.price') from student;

19.95

16. 空格字符串函数：space

语法: space(int n)

返回值: string

说明：返回长度为n的字符串

举例：

hive> select space(10) from student;

（10个空格）

hive> select length(space(10)) from student;

10

17. 重复字符串函数：repeat

语法: repeat(string str, int n)

返回值: string

说明：返回重复n次后的str字符串

举例：

hive>  select repeat('abc|',5) from student;

abc|abc|abc|abc|abc|

18. 首字符ascii函数：ascii

语法: ascii(string str)

返回值: int

说明：返回字符串str第一个字符的ascii码

举例：

hive> select ascii('abcde') from student;

97

19. 左补足函数：lpad

语法: lpad(string str, int len, string pad)

返回值: string

说明：将str进行用pad进行左补足到len位

举例：

hive> select lpad('abc',10,'td') from student;

tdtdtdtabc

--注意：与GP，ORACLE不同，pad 不能默认

hive> select lpad('abc',4,'td') from student;

tabc

20. 右补足函数：rpad

语法: rpad(string str, int len, string pad)

返回值: string

说明：将str进行用pad进行右补足到len位

举例：

hive> select rpad('abc',10,'td') from student;

abctdtdtdt

21. 分割字符串函数: split

语法: split(string str, string pat)

返回值: array

说明: 按照pat字符串分割str，会返回分割后的字符串数组

举例：

hive> select split('abt,cdt,ef',',') from student;

["abt","cdt","ef"]

22. 集合查找函数: find_in_set

语法: find_in_set(string str, string strList)

返回值: int

说明: 返回str在strlist第一次出现的位置，strlist是用逗号分割的字符串。如果没有找该str字符，则返回0

举例：

hive> select find_in_set('ab','ef,ab,de') from student;

2

hive> select find_in_set('at','ef,ab,de') from student;

0

23.查找字符串在某个字符串当中的开始位置 instr

语法：instr(string str string str2);

返回值: int

说明：返回 str2在str 中的开始位置，两个参数有一个为null则返回null

hive> select instr("abcd" "ab");

0