SQL: How to select all parent nodes in Materialized path?

问题

The MySQL databse stores tree with the help of materialized path data structure. How to select all parents of the given node?

I use dot '.' as path separator, and database structure includes 'level' field that indicates the depth of a node in the tree.

Lets I have those tree and need all parents of the node 'a.b.d.e':

id | path
 a | a
 b |  a.b
 c |   a.b.c
 d |   a.b.d
 e |    a.b.d.e
 f |  a.f

The script should return:

a
a.b
a.b.d
a.d.d.e (optional)

How to do that in MySQL?

回答1:

I've found the solution in the question posted by @quambo. Here it is:

SELECT * FROM table
WHERE ? LIKE id||%
ORDER BY path

Insted of '?' it is necessary to place the path to the given node.

SELECT * FROM table
WHERE 'a.b.d.e' LIKE id||%
ORDER BY path

来源：https://stackoverflow.com/questions/41783113/sql-how-to-select-all-parent-nodes-in-materialized-path