Home/ Questions/Q 573851
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-13T13:46:06+00:00

I’m storing linked lists of data in records that look like this: CREATE TABLE

  • 0

I’m storing linked lists of data in records that look like this:

CREATE TABLE IF NOT EXISTS `data_nodes` (
  `record_id` int(11) NOT NULL,
  `prev_node` int(11) NOT NULL,
  `data` varchar(200) NOT NULL,
  PRIMARY KEY  (`record_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;

where prev_node is the record_id of the previous item in the list, or 0 if we’re at the first item in the list.

A typical list might look something like :

record_id     prev_node     data
---------     ---------     ----
1             0             first item
12            1             second item
27            12            third item

I’m using Ruby’s mysql module, and what I’d like to do is: given the record number of the last item in a list, load the entire list in a single query. (e.g. given the record id 27, return a result set that contains “first item”, “second item”, “third item”)

Can this be done?

Thanks.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    It’s possible for tree of any fixed height N, but you won’t be able to do this operation, if tree height becomes N+1.

    In other words, if you know how many levels of parent/child nodes there are, you may build a query as explained here (search for Retrieving a Single Path): http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/

    You may use nested set model and RoR plugin acts_as_nested_set to get the results you want.

    If you need help on the article, let know.

    • 0