MySQL: Query Real Values from Delimiter-Separated-String-IDs

Chaoz — Mon, 15 Sep 2008 14:15:37 +0000

I had a problem in using a string-comma-separated-value returned from a query in an “IN” statement. I used the IDs from one table, concat them into a comma separated value and insert them into another table. Baaaad idea… Now when I query that value, I can’t use it directly into an “IN” statement to retrieve their real values since its a string being returned from the query, the “IN” statement will not compare all the values inside as a set, but it will compare it as a string.

e.g.
SELECT value FROM my_table WHERE my_id IN (’1, 2, 3′) is NOT equivalent to SELECT value FROM my_table WHERE my_id IN (’1′, ’2′, ’3′)

So, if you have a table containing values 1 to 3, the first query will return only 1 while the second query will return all values; 1, 2 and 3.

I Googled around and found out that MySQL does not have a native equivalent of PHP’s explode() function. Crap… I had to do it the hard war and create a MySQL stored function to ‘explode’ the values from its delimiter, query the right value from the other table using the exploded IDs, concat them back together and return them as a string.

Below is the function I was able to patch together from different codes I found in the MySQL forum. I added comments below as to make things clearer. I named the function splitAndTranslate since that’s what I was really trying to implement. You can make up your own modifications and function name.

DELIMITER //
DROP FUNCTION IF EXISTS `splitAndTranslate` //
CREATE FUNCTION splitAndTranslate(str TEXT, delim VARCHAR(124))
RETURNS TEXT
DETERMINISTIC
BEGIN
	DECLARE i INT DEFAULT 0;	-- total number of delimiters
	DECLARE ctr INT DEFAULT 0;	-- counter for the loop
	DECLARE str_len INT;		-- string length,self explanatory
	DECLARE out_str text DEFAULT '';	-- return string holder
	DECLARE temp_str text DEFAULT '';	-- temporary string holder
  	DECLARE temp_val VARCHAR(255) DEFAULT '';	-- temporary string holder for query
 
	-- get length
	SET str_len=LENGTH(str);	
 
	SET i = (LENGTH(str)-LENGTH(REPLACE(str, delim, '')))/LENGTH(delim) + 1;	
		-- get total number delimeters and add 1
		-- add 1 since total separated values are 1 more than the number of delimiters
 
	-- start of while loop
	WHILE(ctr<i) DO
		-- add 1 to the counter, which will also be used to get the value of the string
		SET ctr=ctr+1; 
 
		-- get value separated by delimiter using ctr as the index
		SET temp_str = REPLACE(SUBSTRING(SUBSTRING_INDEX(str, delim, ctr), LENGTH(SUBSTRING_INDEX(str, delim,ctr - 1)) + 1), delim, '');
 
		-- query real value and insert into temporary value holder, temp_str contains the exploded ID    		
		SELECT <real_value_column> INTO temp_val FROM <my_table> WHERE <table_id>=temp_str;
 
		-- concat real value into output string separated by delimiter
    		SET out_str=CONCAT(out_str, temp_val, ',');
	END WHILE;
	-- end of while loop
 
	-- trim delimiter from end of string
	SET out_str=TRIM(TRAILING delim FROM out_str);
	RETURN(out_str);	-- return 
 
END//

After creating the stored function, you can now use it normally like any MySQL function inside a query. So what I now do with the new function is…

SELECT splitAndTranslate( g.comma_separated_ids ) real_values FROM my_group_table g;

Thanks to Chris Stubben in the MySQL Forum, I used and modified his code to fit my need.

Friendster Script

Chaoz — Mon, 13 Aug 2007 16:56:51 +0000

Well, seems like a problem crept into a friend’s Friendster account. Everything in her page disappeared, or so it seems. The problem lay inside the shoutbox. A rouge script has inserted a small CSS script inside and made every “Div” element invisible. How? I dont know. I made this script for her to run under greasemonkey. This will rewrite what’s inside the shoutbox and let her rewrite whats inside back to normal.

The greasemonkey script can be found under the script page or here.

SlickDev » Scripts

MySQL: Query Real Values from Delimiter-Separated-String-IDs

Friendster Script