help with nested set

#11

lawpoop <lawpoop (AT) gmail (DOT) com> wrote:

Quote:

On Apr 13, 9:27*am, paul c <toledobythe... (AT) oohay (DOT) ac> wrote:
lawpoop wrote:

...

Suppose I had this adjacency list:

id *client_id parent_id level
1 * * * 1 * * * *NULL * * *Corporate
2 * * * 1 * * * * *1 * * * Franchise 1
4 * * * 1 * * * * *1 * * * Eastern Region
5 * * * 1 * * * * *4 * * * New York District
...

Can't comment on product techniques but if this were a 'table', I'd
wonder how a client can be its own parent. *I would have thought some
constraint would prevent that.

Are you asking why all of these example rows have a value for the
client_id? Are you saying it should look like this? :

id client_id parent_id level
1 1 NULL Corporate
2 NULL 1 Franchise 1
4 NULL 1 Eastern Region
5 NULL 4 New York District

MySQL check constraints are somewhat limited; what would you suggest?

Remove the null.

Entity
id *client_id level
1 * * * 1 * * *Corporate
2 * * * 1 * * *Franchise 1
4 * * * 1 * * *Eastern Region
5 * * * 1 * * *New York District

ParentEntity
id parent_id
2 1
4 1
5 4

Since Corporate does not have a parent, it does not have a row
in the ParentEntity table.

Computerese Irregular Verb Conjugation:
I have preferences.
You have biases.
He/She has prejudices.

#12

On Apr 16, 4:13*pm, Gene Wirchenko <ge... (AT) ocis (DOT) net> wrote:

Quote:

Entity
id *client_id *level
1 * * * 1 * * *Corporate
2 * * * 1 * * *Franchise 1
4 * * * 1 * * *Eastern Region
5 * * * 1 * * *New York District

ParentEntity
id *parent_id
2 * * *1
4 * * *1
5 * * *4

* * * Since Corporate does not have a parent, it does not have a row
in the ParentEntity table.

Clever.

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help with nested set

comp.databases.theory comp.databases.theory

Re: help with nested set - 04-16-2009 , 06:13 PM

Re: help with nested set - 04-20-2009 , 12:20 PM