MySQL : Cascade update on same table - mysql

Question

I have a MySQL table in which each records references its parent_id :
| id | Summary | parent_id | hidden |
-------------------------------------
| 1 | First | NULL | 0 |
| 2 | Hello | 1 | 0 |
| 3 | john | 1 | 0 |
| 4 | Second | NULL | 0 |
| 5 | World | 2 | 0 |
| 6 | Doe | 4 | 0 |
I would like to cascade update so that if line 1 becomes hidden, its child (line 2) and the childs of its childs (line 5) becomes also hidden.
Is it possible with MySQL.
I already have a DELETE ON CASCADE constraint which works fine.
CONSTRAINT FK_ID_With_CascadeDelete FOREIGN KEY (parent_id) REFERENCES MyTable (id) ON DELETE CASCADE

Answer 1

You can use Stored Procedure as follows.
DELIMITER $$
DROP PROCEDURE IF EXISTS `update_node`$$
CREATE PROCEDURE `update_node`(IN p_id INT)
proc: BEGIN
DECLARE e_no_id CONDITION FOR SQLSTATE '45000';
IF ( p_id IS NULL ) THEN
SIGNAL e_no_id SET MESSAGE_TEXT = 'The id cannot be empty.';
LEAVE proc;
END IF;
DROP TEMPORARY TABLE IF EXISTS del_temp_table;
CREATE TEMPORARY TABLE IF NOT EXISTS del_temp_table(
id INTEGER UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
delids INTEGER UNSIGNED NOT NULL,
node INTEGER DEFAULT 0
);
SET #rept := #loopcount := 1;
INSERT INTO del_temp_table (delids, node) SELECT p_id, #rept;
myloop: WHILE (1 = 1)
DO
SELECT COUNT(id) AS cnt FROM test WHERE `parent_id` IN ( SELECT DISTINCT(delids) FROM del_temp_table WHERE node = #rept ) INTO #loopcount;
IF (#loopcount = 0) THEN
LEAVE myloop;
ELSE
SET #rept := #rept + 1;
SELECT GROUP_CONCAT(d1.delids) INTO #wherein FROM ( SELECT DISTINCT(delids) FROM del_temp_table WHERE node = (#rept - 1) ) AS d1;
INSERT INTO del_temp_table (delids, node) SELECT id, #rept FROM test WHERE FIND_IN_SET( parent_id, #wherein ) > 0;
END IF ;
END WHILE myloop;
UPDATE test SET hidden = 1 WHERE id IN ( SELECT delids FROM del_temp_table );
END$$
DELIMITER ;
Here i used Temporary table to store recursive nodes and iterated each time by using that table to fetch next child and inserted it into same table.
I believe this could help you. Replace table name test with your table name

Answer 2

I think you simply can't do that. Even with an UPDATE TRIGGER you cannot update other rows on the same table.
Maybe this is not the answer you were expecting but probably your best choice is to use a PROCEDURE like this:
DELIMITER //
CREATE PROCEDURE UpdateHiden(IN pid INT, IN phidden INT)
BEGIN
UPDATE mytable
SET HIDDEN = phidden
WHERE ID = pid OR parent_id = pid;
END; //
DELIMITER ;
See sample on DB Fiddle here