Thanks, Erik, for your idea.
And if I create a method to dynamically set the path?(to eliminate the problem of reallocating categories?)
I will try right now.
Thank you again.
At 15:35 -0200 10/31/00, Nilton Lessa wrote:
>I am trying to build a database with 2 Tables;
>1- Table 1 {name, URL, objectPRT to Table 2}
>
>2- Table 2{category, desciption, objectPTR to self} , trying to implement
>subcategory, subsubcategory,and so on.
>
>Suppose that I have on Table 2:
>Category A
>Category B points to A (subcategory of A)
>Category C point to B (subcategory of B)
>
>And on Table 1:
>Record1 points to CAtegory C.
>
>I would like to be able to find this record even if I search by Category B
>(its father) or Category A(its grandfather), and so on.
>
>Is it possible to construct a SQL command to do this?
Hi, Nilton --
I do something much like this in one of my applications. I had to keep
track of not only the fact that B and C were subcategories of A, but also
the ordering of the categories; e.g., that B as a category came between A
and B.
I did this by creating a VarChar field called "path" which contains the
hierarchical path of the category record. So the record for Category C in
your example would have a path of:
A B C
If you index this field by word, then you can search for "B" and find the
records for categories B and C in your example.
In my case, I use the first few letters of a category's full name for its
path element, so new subcategories will, if sorted by path, sort properly
in with existing ones.
When I create a new category, I simply assign its parent category, and the
whole path is then inferred from there.
This approach works splendidly in all ways, and I have been very pleased
with it. The only drawback that I can think of is that it would be
difficult to shift your hierarchy around if you decided that some
subcategories really belonged under different parent categories.
Hope this helps,
Erik
______________________________________________________________________
Erik D. Mueller-Harder, Editor Praxis News Digest
http://pnd.praxisworks.com/
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