Tokenize a delimited string in MySQL - mysql

Question

I wrote a function in MySQL to split a delimited string into tokens, but right now, it only returns the first token it encounters after the start position (pos). Is there a way to get it to return tokens as a result set with one column containing all of the parsed tokens?
Here is my current function code:
CREATE DEFINER=`root`#`localhost` FUNCTION `split_string_multi_byte`(
source_string VARCHAR(255),
delim VARCHAR(12),
pos INT) RETURNS varchar(255) CHARSET latin1
BEGIN
RETURN REPLACE(SUBSTRING(SUBSTRING_INDEX(source_string, delim, pos),
CHAR_LENGTH(SUBSTRING_INDEX(source_string, delim, pos -1)) + 1),
delim, "");
END
Here are some parameters that I entered in my Navicat database development and admin client:
That returns the following results:
See how only "1" is returned. I would like to see all of the tokens if possible. However, I'm not sure how to do that.
Any help would be appreciated.
Thanks!
Rob

Answer 1

CREATE DEFINER=`root`#`%` FUNCTION `SPLIT`(s varchar(200), c char, i integer) RETURNS varchar(200) CHARSET utf8mb4
DETERMINISTIC
BEGIN
DECLARE retval varchar(200);
WITH RECURSIVE split as (
select 1 as x,substring_index(substring_index(s,c,1),c,-1) as y, s
union all
select x+1,substring_index(substring_index(s,c,x+1),c,-1),s from split where x<= (LENGTH(s) - LENGTH(REPLACE(s,c,'')))
)
SELECT y INTO retval FROM split WHERE x=i ;
return retval;
END
SELECT SPLIT('a,b,c,d,e,f',',',3); results in 'c'
Because you cannot return a table from a function (in MySQL), you could do something like this if you want results in a table:
SET #tekst = 'aap,noot,mies,wim,zus,jet';
WITH RECURSIVE abc as (
SELECT 1 as c
UNION ALL
SELECT c+1
FROM abc WHERE c<=15)
select c,split(#tekst,',',c) as t
from abc
where not split(#tekst,',',c) is null;
output:
+------+------+
| c | t |
+------+------+
| 1 | aap |
| 2 | noot |
| 3 | mies |
| 4 | wim |
| 5 | zus |
| 6 | jet |
+------+------+