mysql procedure for counting comma delimited varchar

tag_count.sql

-- base table 
CREATE TABLE IF NOT EXISTS tags (
	id INT PRIMARY KEY AUTO_INCREMENT, 
	tags VARCHAR(128)
);

-- prepare data 
INSERT INTO tags(tags) VALUES (",3,47,1,5,"), ("1,2,3"), (",4,5,6,7"), ("3,4,6,");

-- create procedure 
DROP PROCEDURE IF EXISTS tag_cnt; 
DELIMITER //
CREATE PROCEDURE tag_cnt()
BEGIN 
	DECLARE ts VARCHAR(128);
	DECLARE done INT DEFAULT FALSE;
	DECLARE cur CURSOR FOR SELECT concat(',', tags, ',') FROM tags;
	DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

	OPEN cur;
	
	-- create temp table for counting
	CREATE TEMPORARY TABLE IF NOT EXISTS tag_cnt  (
		tag VARCHAR(128) PRIMARY KEY,
		cnt INT DEFAULT 0
	);

	-- clear table 
	TRUNCATE TABLE tag_cnt; 

	each_row: LOOP
		FETCH cur INTO ts;
		IF done THEN LEAVE each_row; END IF;

		SET @start = locate(',', ts);
		each_field: LOOP
			SET @end = locate(',', ts, @start + 1);

			-- no more tag
			IF @end = 0 THEN LEAVE each_field; END IF;

			IF @end <> @start+1 THEN 
			      SET @t = trim( substring(ts, @start + 1, @end - @start -1) );	
			      INSERT INTO tag_cnt SET tag = @t ON DUPLICATE KEY UPDATE cnt = cnt + 1;
			END IF; 

			SET @start = @end;
		END LOOP each_field; 

	END LOOP each_row;

	CLOSE cur;
END 
//
DELIMITER ;

CALL tag_cnt();
SELECT * FROM tag_cnt;