How to remove multi-level menu item with children in MySQL? - php

Question

I have unlimited level menu structure in MySQL, where parent and children elements are connected with column p_id:
+----+------+------+----------------+
| id | p_id | sort | name_en |
+----+------+------+----------------+
| 1 | 0 | 1 | menu-1 |
| 2 | 0 | 2 | menu-2 |
| 3 | 0 | 6 | menu-3 |
| 4 | 2 | 3 | sub-menu-2-1 |
| 5 | 2 | 4 | sub-menu-2-2 |
| 6 | 5 | 5 | sub-menu-2-2-1 |
+----+------+------+----------------|
What is best practice for deleting root menu element with sub-menu elements?
I can achieve it with PHP recursion, but it will cause some number of queries.
So I need to find out if is there any possible way to do it with one MySQL query.

Answer 1

Since you have name_en, cannot you use that one to delete the rows? For example,
DELETE FROM `table` WHERE `id` = 2 OR `name_en` LIKE 'sub-menu-2-%'
New method:
You can use a Foreign Key with a constraint. I created your table and called it treelist,
CREATE TABLE `treelist` (
`item_id` int(10) unsigned NOT NULL auto_increment,
`parent_id` int(10) unsigned default NULL,
`name_en` varchar(40) NOT NULL,
PRIMARY KEY (`item_id`),
KEY `FK_parent_id` (`parent_id`),
CONSTRAINT `FK_parent_id` FOREIGN KEY (`parent_id`) REFERENCES `treelist` (`item_id`) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
I then added some test data, the ones you had in your question,
INSERT INTO `treelist` (`item_id`, `parent_id`, `name_en`) VALUES (NULL, NULL, 'Menu 1'), (NULL, NULL, 'Menu 2'), (NULL, NULL, 'Menu 3'), (NULL, 2, 'Sub Menu 2-1'), (NULL, 2, 'Sub Menu 2-2'), (NULL, 5, 'Sub Menu 2-2-1');
Now, when you delete a row, for example
DELETE FROM `treelist` WHERE `item_id` = 2
It will delete all children, grand-children etc as well. Afterwards the table looks like,
+----+------+----------------+
| id | p_id | name_en |
+----+------+----------------+
| 1 | NULL | Menu 1 |
| 3 | NULL | Menu 3 |
+----+------+----------------+

Answer 2

To delete just a row and it's direct children (not grandchildren):
DELETE FROM tablename where id = 1 or p_id = 1;
UPDATE 1:
If you have freedom to add a column to the table, you could add root_id and easily do the delete based on that. This will not ruin any current queries in your system and will only take a one-time run of a simple script to add the initial data.
DELETE FROM tablename where id = 1 or root_id = 1;
UPDATE 2:
A pretty awesome option is that foreign keys to the same table are allowed. So you can add a foreign key to p_id that references id, use on delete cascade and when you delete the root, all descendants will be removed also. I created a test table and this worked beautifully for me. It may also be beneficial to add on update cascade. Remember that p_id as well as id need to be unsigned for this to work.
ALTER TABLE tablename ADD CONSTRAINT fk_tablename_id FOREIGN KEY (p_id) references tablename(id) ON DELETE CASCADE;

Answer 3

Just category id or parent id in first parameter:
function delete_parent_and_child_subchild($category_id,$all_cate=array())
{
if(!is_array($category_id))
{
$this->db->where('parent_id', $category_id);
$all_cate[]=$category_id;
}
else
{
$this->db->where_in('parent_id', $category_id);
}
$get_categories= $this->db->get('newcategory');
if($get_categories->num_rows()>0)
{
$categories_vales=$get_categories->result();
$new_subcat = array();
foreach($categories_vales as $cate_val)
{
$category_id=$cate_val->category_id;
array_push($new_subcat,$category_id);
}
$all_cate = array_merge($all_cate,$new_subcat);
if(count($new_subcat)>0)
{
$this->delete_parent_and_child_subchild($new_subcat,$all_cate);
}
}
$this->db->where_in('category_id', $all_cate)->delete('newcategory');
return true;
}