I have a database table which link locations together; a location can be in a location, which can be inside another location.
location (<id>, ....)
location_parent (<location_id>, <parent_id>)
Here's the MySQL/PHP to go down for a depth of one:
$sql = "SELECT id FROM se_locations_services WHERE parent_locationid IN
( SELECT location_id FROM se_locations_parent WHERE parent_id = '$locationid' )";
How do I, given a parent location, gets all its descendants locations, no matter how deep, just using MySQL?
There's a good-looking article over at mysql.com outlining various ways of managing hierarchical data. I think it provides a full solution to your question, and shows various less simple, but faster approaches (e.g. Nested Sets).
MySQL lacks native support of hierarchical functions, so you'll have to emulate them using session variables to keep the recursion state.
See this article on how to implement the function:
A much better way of managing this sort of data is to use the Modified Preorder Tree Traversal technique:
http://articles.sitepoint.com/article/hierarchical-data-database/2
hth
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Since mysql statements can return only table-structured data, how do you imagine the returned tree-structure?
It is possible to do a selection with [parent_id, child_id] table, but it requires temporary table and I've seen it done on DB2, not on MySQL.
Check this article for implementation on tree-like structures stored in MySQL: http://articles.sitepoint.com/article/hierarchical-data-database/
来源：https://stackoverflow.com/questions/2378678/mysql-recursing-a-tree-structure