Hive字符串处理

截取

Return Type	Name(Signature)	Description
string	substr(string A, int start)	Returns the substring or slice of the byte array of A starting from start position till the end of string A. For example, substr(‘foobar’, 4) results in ‘bar’ …对于字符串A,从start位置开始截取字符串并返回
string	substr(string A, int start, int len)	Returns the substring or slice of the byte array of A starting from start position with length len. For example, substr(‘foobar’, 4, 1) results in ‘b’ …对于二进制/字符串A,从start位置开始截取长度为length的字符串并返回
string	substring_index(string A, string delim, int count)	Returns the substring from string A before count occurrences of the delimiter delim (as of Hive 1.3.0). If count is positive, everything to the left of the final delimiter (counting from the left) is returned. If count is negative, everything to the right of the final delimiter (counting from the right) is returned. Substring_index performs a case-sensitive match when searching for delim. Example: substring_index(‘www.apache.org’, ‘.’, 2) = ‘www.apache’…截取第count分隔符之前的字符串，如count为正则从左边开始截取，如果为负则从右边开始截取
int	instr(string str, string substr)	Returns the position of the first occurrence of substr in str. Returns null if either of the arguments are null and returns 0 if substr could not be found in str. Be aware that this is not zero based. The first character in str has index 1…查找字符串str中子字符串substr出现的位置，如果查找失败将返回0，如果任一参数为Null将返回null，注意位置为从1开始的

拼接

Return Type	Name(Signature)	Description
string	concat(string A, string B…)	Returns the string or bytes resulting from concatenating the strings or bytes passed in as parameters in order. For example, concat(‘foo’, ‘bar’) results in ‘foobar’. Note that this function can take any number of input strings…对二进制字节码或字符串按次序进行拼接
string	concat_ws(string SEP, string A, string B…)	Like concat() above, but with custom separator SEP…与concat()类似，但使用指定的分隔符喜进行分隔
string	concat_ws(string SEP, array<string>)	Like concat_ws() above, but taking an array of strings. (as of Hive 0.9.0).拼接Array中的元素并用指定分隔符进行分隔

1. concat()

2. concat_ws()

指定分隔符将多个字符串连接起来，结合group by与collect_set使用可实现“列转行”。

hive > select concat_ws('+','a','b','c');
OK
a+b+c

hive > select aa, bb, cc from jj_tmp.user_list;
OK
c	d	1
c	d	2
c	d	3
e	f	4
e	f	5
e	f	6

hive > select aa, bb, concat_ws(',' , collect_set(cast(cc as string