Infinite level classification (or menu) design

id	title	path	level	paths
1	clothing	0	0	0,1
2	jacket	0,1	1	0,1,2
7	shirt	0,1,2	2	0,1,2,7
3	The trousers	0,1	1	0,1,3
4	Trousers for	0,1,3	2	0,1,3,4
5	Long trousers	0,1,3,4	3	0,1,3,4,5
6	Short trousers	0,1,3,4	3	0,1,3,4,6

among ,path Represents the parent id list . For example, trousers 0,1,3 It means clothes > The trousers
Just take out the bread crumbs path Value of field , And then use , Division , obtain id list
Reuse where id in (1,3) that will do

When it is necessary to display all categories and represent levels , Use the following SQL：

SELECT *,concat(path,',',id) AS paths FROM menu ORDER BY paths