Implementing a set of nested orders in MySQL / PHP

Question

I am trying to create a database in which there can be a nnumber of categories, as well as their subcategories.

At first I tried to create an adjacency model database like this

+-------------+----------------------+--------+
| category_id | name                 | parent |
+-------------+----------------------+--------+
|           1 | Electronics          |   NULL |
|           2 | Mobile               |      1 |
|           3 | Washing Machine      |      1 |
|           4 | Samsung              |      2 |
+-------------+----------------------+--------+

but I ran into a problem when deleting a node, for example, how to manage child nodes for remote nodes, etc.

then I'm trying to implement the Nested Order Set Joe Celko

The table structures in each figure:

Figure 1:
+----+-------------+-----+-----+
| id | name        | lft | rgt |
+----+-------------+-----+-----+
| 1  | Electronics | 1   | 2   |
+----+-------------+-----+-----+

Figure 2:
+----+-------------+-----+-----+
| id | name        | lft | rgt |
+----+-------------+-----+-----+
| 1  | Electronics | 1   | 4   |
+----+-------------+-----+-----+
| 2  | Mobile      | 2   | 3   |
+----+-------------+-----+-----+

Figure 3:
+----+-----------------+-----+-----+
| id | name            | lft | rgt |
+----+-----------------+-----+-----+
| 1  | Electronics     | 1   | 6   |
+----+-----------------+-----+-----+
| 2  | Mobile          | 2   | 3   |
+----+-----------------+-----+-----+
| 3  | Washing Machine | 4   | 5   |
+----+-----------------+-----+-----+

Figure 4:
+----+-----------------+-----+-----+
| id | name            | lft | rgt |
+----+-----------------+-----+-----+
| 1  | Electronics     | 1   | 8   |
+----+-----------------+-----+-----+
| 2  | Mobile          | 2   | 5   |
+----+-----------------+-----+-----+
| 3  | Washing Machine | 6   | 7   |
+----+-----------------+-----+-----+
| 4  | Samsung         | 3   | 4   |
+----+-----------------+-----+-----+

but I cannot insert a new node with the correct rgtand lft. I use this, but it does not generate the correct values rgtand lft.

LOCK TABLE nested_category WRITE;

SELECT @myRight := rgt FROM nested_category
WHERE name = 'Mobile';

UPDATE nested_category SET rgt = rgt + 2 WHERE rgt > @myRight;
UPDATE nested_category SET lft = lft + 2 WHERE lft > @myRight;

INSERT INTO nested_category(name, lft, rgt) VALUES('LG', @myRight + 1, @myRight + 2);

UNLOCK TABLES;

Answer 1

http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/ - , ?

, add a brother node.

add a child node:

LOCK TABLE nested_category WRITE;

SELECT @myLeft := lft FROM nested_category
WHERE name = 'Mobile';

UPDATE nested_category SET rgt = rgt + 2 WHERE rgt > @myLeft;
UPDATE nested_category SET lft = lft + 2 WHERE lft > @myLeft;

INSERT INTO nested_category(name, lft, rgt) VALUES('LG', @myLeft + 1, @myLeft + 2);

UNLOCK TABLES;

Answer 2

CREATE PROCEDURE nested_insert(_name VARCHAR(45))
BEGIN
DECLARE _number int;
set @var=0;

-- first insert paramater value(_name) into nested_table
INSERT into nested_table(name) VALUE(_name);

-- count the total row  value from nested table;
SELECT count(*) from  nested_table into _number;

-- first update the all lft column from top to button by varibale with increment
UPDATE nested_table set lft=(@var:=@var+1) where id <=_number;

-- second update the all rgt column from button to top by varibale with increment in descending order id
UPDATE nested_table set rgt=(@var:=@var+1) where id<=(_number+1)*2 ORDER BY id desc ;
end;