如何在 MySQL 中删除带有子项的多级菜单项？

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;
        }