Trong database chúng trông như sau: id | parent_id | lft | rgt | depth | data 1 | | 1 | 14 | 0 | root 2 | 1 | 2 | 7 | 1 | Child 1 3 | 2 | 3 | 4 | 2 | Child 1.1 4 | 2 | 5 | 6 | 2 | Child 1.2 5 | 1 | 8 | 13 | 1 | Child 2 6 | 5 |...