Building Hierarchical Tree

From parent child table

[ukgimp]

Hello

Is it difficult to build a hierarchical tree from a table that has a parent field. Imagine that the table was:

Cat ¦ Parent
1¦ null
2¦1
3¦1
4¦3
5¦3
6¦1

is it difficult to get the following:

1
--2
--3
----4
----5
--6

If possible does anyone know of and good examples of this online so I can learn from it.

Cheers

[jpjones]

I'm looking into doing this myself over the next couple of days. A quick google for "php hierarchical tree" brings up a few resources. Number 1 result at DevShed looks like it'll help you to do what you want.

JP

[ukgimp]

Cheers jp

I was looking through devshed and found a recursive query, but there was a commemt whic hmade me think twice

this is not an efficient algorithm
* because it has to issue one query per category!

That worries me :)

There has to be a slick way of doing it.

[magicke]

hmm...

Slicker would be to incorporate each record's heirarchy level in a system-assigned id field (if thats not in your table definition yet).

You could then do an str_repeat("-", <heirarchylevel>) in the resultset display loop, like so...

while (!eof) {
echo str_repeat("&nbsp;", sqlresultset->fields("hLevelID"));
echo sqlresultset->fields("AcctID")."<br>\n";
}

It'd cost you a few bytes per record, but does allow you to do the formatting with a single query.

magicke

[dmorison]

How big is your tree going to be?

If not too big just read the table in one go and do whatever you want with the array in memory.