David,

<snip>
>I can easily substitute integers from my primary key for
>names, but how do I substitute them for parents? For example:

>ID | NAME | PARENT
>10 | Canidae | Carnivora
>11 | Canis | Canidae
>12 | Vulpes |Canidae

>I can easily replace Canis with 11, Vulpes with 12.
>But they both have the same family - Canidae, which
>translates as 10. I could create a new field and
>manually, like this:

>ID | NAME | PARENT | PARENTID
>10 | Canidae | Carnivora | 9
>11 | Canis | Canidae | 10
>12 | Vulpes |Canidae | 10

>But if I add or delete a row, the numerals in my
>primary key will change,


No. Existing autosequential (auto-increment) values are not affected by new autosequential values.

One argument for keeping each level in its own table is the possibility of cleanly enforcing referential integrity, eg a constraint that prevents deletion of a parent row which is referenced in a row of a child tabke.

>messing up the values in
>PARENTID.


No. See above.

>Consider the database table code below, which displays
>animal names (representing all taxonomic heirarchies)
>in a child-parent relationship:

>ID | NAME | PARENT
>1 | Mammalia | (NULL)
>2 | Carnivora | Mammalia
>3 | Canidae | Carnivora
>4 | Canis | Canidae
>5 | leo | Canis
>6 | Felidae | Carnivora
>7 | Panthera | Felidae
>8 | leo | Panthera


Sorry, what do you mean by 'database table code'? What I see is a text representation of some rows from a table.

>Rows 5 and 8 represent identical species names, leo.
>If I type http://geozoo/stacks/leo/ into my browser,
>it defaults to Mammalia > Carnivora > Canidae > Canis
>> leo, rather than the lion, Mammalia > Carnivora >
>Felidae > Panthera > leo

>So I need a way to distinguish one leo from the other.


I gather yuou have some code that reads what the user types in and tries to complete her request sentence. For the cases where the last name she typed is the name of more than one entity, you need to provide the user an interface for making a choice. One possibility for the case you instance would be a dropdown miniwindow which collects the possibilities, here leo (Canis) or leo (Panthera), and puts them in a dropdown for her to choose. Another possibility is to put up a page or frame that represents the bit of the tree that the user has so far specified, plus one level, and let her walk down the tree.

>Would it be possible to somehow combine my
>auto-incrementing primary key with the field Name,
>converting leo / leo to 5leo / 8leo?

Sure. You can query on anything you please, and show any part of that query, or all of it, or none of it.

>There are two things I'd have to deal with...

>1. I'd need to weed the numerals out of the display,
>which should look like this...

Sure. The user shouldn't have to be bothered with the details of how you make her job easier.

I do not understand why you think your autoincrement values need to change. The whole idea is that, once assigned, they _never_ change. If your update model entails changing primary keys, fix the model.

PB

-----

David Blomstrom wrote:
--- Peter Brawley <peter.brawley@earthlink.net> wrote:

"As you note, the names [of animal taxons] aren't
guaranteed to be unique, or to stay the same . . .
 
  
One way out is to give every table an
auto-incrementing integer PK, and 
use those keys, which will never change, to mark
parent-child relationships.
    

I wanted to follow up on this. I can easily substitute
integers from my primary key for names, but how do I
substitute them for parents? For example:

ID | NAME | PARENT
10 | Canidae | Carnivora
11 | Canis | Canidae
12 | Vulpes |Canidae

I can easily replace Canis with 11, Vulpes with 12.
But they both have the same family - Canidae, which
translates as 10. I could create a new field and
manually, like this:

ID | NAME | PARENT | PARENTID
10 | Canidae | Carnivora | 9
11 | Canis | Canidae | 10
12 | Vulpes |Canidae | 10

But if I add or delete a row, the numerals in my
primary key will change, messing up the values in
PARENTID.

Along similar lines, I have another question...

Consider the database table code below, which displays
animal names (representing all taxonomic heirarchies)
in a child-parent relationship:

ID | NAME | PARENT
1 | Mammalia | (NULL)
2 | Carnivora | Mammalia
3 | Canidae | Carnivora
4 | Canis | Canidae
5 | leo | Canis
6 | Felidae | Carnivora
7 | Panthera | Felidae
8 | leo | Panthera

Rows 5 and 8 represent identical species names, leo.
If I type http://geozoo/stacks/leo/ into my browser,
it defaults to Mammalia > Carnivora > Canidae > Canis
  
leo, rather than the lion, Mammalia > Carnivora >
    
Felidae > Panthera > leo

So I need a way to distinguish one leo from the other.

Would it be possible to somehow combine my
auto-incrementing primary key with the field Name,
converting leo / leo to 5leo / 8leo?

There are two things I'd have to deal with...

1. I'd need to weed the numerals out of the display,
which should look like this...

<a href="http://geozoo/stacks/leo/">leo</a>

not this...

<a href="http://geozoo/stacks/8leo/">8leo</a>

2. The numerals would have to be fluid, as I will be
adding and deleting rows. Thus, the lion could be 8leo
one day and 9leo the next.

I can take this to a PHP forum to learn how to
implement it. But I thought someone on this forum
might tell me if it can be done in the first place.

Thanks.


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