SPARK-SQL内置函数之字符串函数

转载请注明转自：http://www.cnblogs.com/feiyumo/p/8763186.html

1.concat对于字符串进行拼接

concat(str1, str2, ..., strN) - Returns the concatenation of str1, str2, ..., strN.

Examples:> SELECT concat('Spark', 'SQL');　　SparkSQL

2.concat_ws在拼接的字符串中间添加某种格式

concat_ws(sep, [str | array(str)]+) - Returns the concatenation of the strings separated by sep.

Examples:> SELECT concat_ws(' ', 'Spark', 'SQL');　　Spark SQL

3.decode转码

decode(bin, charset) - Decodes the first argument using the second argument character set.

Examples: > SELECT decode(encode('abc', 'utf-8'), 'utf-8');　　 abc

4.encode设置编码格式

encode(str, charset) - Encodes the first argument using the second argument character set.

Examples: > SELECT encode('abc', 'utf-8');abc

5.format_string/printf 格式化字符串

format_string(strfmt, obj, ...) - Returns a formatted string from printf-style format strings.

Examples:> SELECT format_string("Hello World %d %s", 100, "days");　　Hello World 100 days

6.initcap将每个单词的首字母变为大写，其他字母小写; lower全部转为小写，upper大写

initcap(str) - Returns str with the first letter of each word in uppercase. All other letters are in lowercase. Words are delimited by white space.

Examples:> SELECT initcap('sPark sql');　　Spark Sql

7.length返回字符串的长度

Examples:> SELECT length('Spark SQL ');　　10

8.levenshtein编辑距离（将一个字符串变为另一个字符串的距离）

levenshtein(str1, str2) - Returns the Levenshtein distance between the two given strings.

Examples:> SELECT levenshtein('kitten', 'sitting');　　 3

9.lpad返回固定长度的字符串，如果长度不够，用某种字符补全，rpad右补全

lpad(str, len, pad) - Returns str, left-padded with pad to a length of len. If str is longer than len, the return value is shortened to len characters.

Examples:> SELECT lpad('hi', 5, '??');　　 ???hi

10.ltrim去除空格或去除开头的某些字符,rtrim右去除，trim两边同时去除

ltrim(str) - Removes the leading space characters from str.

ltrim(trimStr, str) - Removes the leading string contains the characters from the trim string

Examples:

> SELECT ltrim('    SparkSQL   ');　　 SparkSQL
> SELECT ltrim('Sp', 'SSparkSQLS');　　 arkSQLS

11.regexp_extract 正则提取某些字符串，regexp_replace正则替换

Examples:> SELECT regexp_extract('100-200', '(\d+)-(\d+)', 1);　　 100

Examples: > SELECT regexp_replace('100-200', '(\d+)', 'num'); 　　num-num

12.repeat复制给的字符串n次

Examples: > SELECT repeat('123', 2);　　123123

13.instr返回截取字符串的位置/locate

instr(str, substr) - Returns the (1-based) index of the first occurrence of substr in str.

Examples:> SELECT instr('SparkSQL', 'SQL');　　6

Examples:> SELECT locate('bar', 'foobarbar');　　 4

14.space 在字符串前面加n个空格

space(n) - Returns a string consisting of n spaces.

Examples:> SELECT concat(space(2), '1');　　1

15.split以某些字符拆分字符串

split(str, regex) - Splits str around occurrences that match regex.

Examples:> SELECT split('oneAtwoBthreeC', '[ABC]');　　　　　　["one","two","three",""]

16.substr截取字符串，substring_index

Examples:

> SELECT substr('Spark SQL', 5);　　k SQL
> SELECT substr('Spark SQL', -3);　　SQL
> SELECT substr('Spark SQL', 5, 1);　　 k

> SELECT substring_index('www.apache.org', '.', 2);　　 www.apache

17.translate 替换某些字符串为

Examples: > SELECT translate('AaBbCc', 'abc', '123');　　 A1B2C3

18.get_json_object

get_json_object(json_txt, path) - Extracts a json object from path.

Examples:> SELECT get_json_object('{"a":"b"}', '$.a');　　b

19.unhex

unhex(expr) - Converts hexadecimal expr to binary.

Examples:> SELECT decode(unhex('537061726B2053514C'), 'UTF-8');　　 Spark SQL

20.to_json

to_json(expr[, options]) - Returns a json string with a given struct value

Examples:

> SELECT to_json(named_struct('a', 1, 'b', 2));　　 {"a":1,"b":2}
> SELECT to_json(named_struct('time', to_timestamp('2015-08-26', 'yyyy-MM-dd')), map('timestampFormat', 'dd/MM/yyyy'));　　 {"time":"26/08/2015"}
> SELECT to_json(array(named_struct('a', 1, 'b', 2));　　 [{"a":1,"b":2}]
> SELECT to_json(map('a', named_struct('b', 1)));　　{"a":{"b":1}}
> SELECT to_json(map(named_struct('a', 1),named_struct('b', 2)));　　 {"[1]":{"b":2}}
> SELECT to_json(map('a', 1));　　{"a":1}
> SELECT to_json(array((map('a', 1))));　　[{"a":1}]

Since: 2.2.0