What is the opposite of GROUP_CONCAT in MySQL?
csv, format, group-concat, mysql, pivot
Solution
I think it is what you need (stored procedure) : Mysql split column string into rows
DELIMITER $$
DROP PROCEDURE IF EXISTS explode_table $$
CREATE PROCEDURE explode_table(bound VARCHAR(255))
BEGIN
DECLARE id INT DEFAULT 0;
DECLARE value TEXT;
DECLARE occurance INT DEFAULT 0;
DECLARE i INT DEFAULT 0;
DECLARE splitted_value INT;
DECLARE done INT DEFAULT 0;
DECLARE cur1 CURSOR FOR SELECT table1.id, table1.value
FROM table1
WHERE table1.value != '';
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
DROP TEMPORARY TABLE IF EXISTS table2;
CREATE TEMPORARY TABLE table2(
`id` INT NOT NULL,
`value` VARCHAR(255) NOT NULL
) ENGINE=Memory;
OPEN cur1;
read_loop: LOOP
FETCH cur1 INTO id, value;
IF done THEN
LEAVE read_loop;
END IF;
SET occurance = (SELECT LENGTH(value)
- LENGTH(REPLACE(value, bound, ''))
+1);
SET i=1;
WHILE i <= occurance DO
SET splitted_value =
(SELECT REPLACE(SUBSTRING(SUBSTRING_INDEX(value, bound, i),
LENGTH(SUBSTRING_INDEX(value, bound, i - 1)) + 1), ',', ''));
INSERT INTO table2 VALUES (id, splitted_value);
SET i = i + 1;
END WHILE;
END LOOP;
SELECT * FROM table2;
CLOSE cur1;
END; $$
Problem
I seem to come against this problem a lot, where I have data that's formatted like this: ``` +----+----------------------+ | id | colors | +----+----------------------+ | 1 | Red,Green,Blue | | 2 | Orangered,Periwinkle | +----+----------------------+ ``` but I want it formatted like this: ``` +----+------------+ | id | colors | +----+------------+ | 1 | Red | | 1 | Green | | 1 | Blue | | 2 | Orangered | | 2 | Periwinkle | +----+------------+ ``` Is there a good way to do this? What is this kind of operation even called?