Jim, I agree with Humberto in that it does not matter. But, Humberto, I did not understand the rest of what you were trying to say about setting the levels of each sub category. Could you please ellaborate? Thanks. Rodney -----Original Message----- From: programmingblind-bounce@xxxxxxxxxxxxx [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Humberto Rodriguez Sent: Wednesday, September 12, 2007 4:03 PM To: programmingblind@xxxxxxxxxxxxx Subject: RE: Relational Database Design Question - Category Tree Hello Jim: It doesn't matter. The only thing you need to make sure of is that each category has an equal subcategory, to set the level of each category. HTH, Humberto -----Original Message----- From: programmingblind-bounce@xxxxxxxxxxxxx [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of james.homme@xxxxxxxxxxxx Sent: Wednesday, September 12, 2007 3:51 PM To: programmingblind@xxxxxxxxxxxxx Subject: RE: Relational Database Design Question - Category Tree Hi, I have another question about this. Does it really matter which categories are sub categories of others as long as you let things be in multiple categories? Thanks. Jim James D Homme, Usability Engineering Highmark Inc. james.homme@xxxxxxxxxxxx 412-544-1810 "It's more important for me to start to do the right thing than it is to wait until I think I can do it just right." "Rodney Haynie" <RodneyH@xxxxxxxx om> To Sent by: "programmingblind@xxxxxxxxxxxxx" programmingblind- <programmingblind@xxxxxxxxxxxxx> bounce@freelists. cc org Subject RE: Relational Database Design 09/12/2007 11:43 Question - Category Tree AM Please respond to programmingblind@ freelists.org Scenario 1 I would say in that example you would have an editor category, and you would have 2 sub categories; text and html. Editor is the parent category . And Text is a child of Editor, and Html is a child of Editor. 1 parent, 2 children. Scenario 2 Say if you have another category called Browser, and you know there is a text browser and a html browser. Would you want to link the same text child and html child of Editor to the Browser category? So, in this example the end result would be: Editor is a parent category . And Text is a child of Editor, and Html is a child of Editor. Browser is a parent category . And Text is a child of Browser, and Html is a child of Browser. Both Editor and Browser are parents. Text has 2 parents (Editor and Browser). Html has 2 parents (Editor and Browser). Scenario 1 is a 1 to 1 relationship. Scenario 2 is a 1 to many relationship. For your project, with items, categories, and levels of subcategories: Scenario 1 will only need 3 tables. But you can implement it with 4. Scenario 2 would require 4 tables. Thanks. Rodney -----Original Message----- From: programmingblind-bounce@xxxxxxxxxxxxx [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of james.homme@xxxxxxxxxxxx Sent: Wednesday, September 12, 2007 11:07 AM To: programmingblind@xxxxxxxxxxxxx Subject: RE: Relational Database Design Question - Category Tree Hi Rodney, Yes. A Category can belong in another category. For example, a text editor can also be an HTML editor. I picked that example out of mid air. Jim James D Homme, Usability Engineering Highmark Inc. james.homme@xxxxxxxxxxxx 412-544-1810 "It's more important for me to start to do the right thing than it is to wait until I think I can do it just right." "Rodney Haynie" <RodneyH@xxxxxxxx om> To Sent by: "programmingblind@xxxxxxxxxxxxx" programmingblind- <programmingblind@xxxxxxxxxxxxx> bounce@freelists. cc org Subject RE: Relational Database Design 09/12/2007 10:18 Question - Category Tree AM Please respond to programmingblind@ freelists.org Conceptually speaking. In your project, I understand that an item can belong to multiple categories. That is just fine, and you are absolutely correct to want a separate table that links items to categories. Now let me ask: Can a category to belong to multiple categories? Or, does a category only belong to one category. After you answer that, then we can chime in with suggestions. Thanks. Rodney -----Original Message----- From: programmingblind-bounce@xxxxxxxxxxxxx [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of james.homme@xxxxxxxxxxxx Sent: Wednesday, September 12, 2007 7:53 AM To: programmingblind@xxxxxxxxxxxxx Subject: RE: Relational Database Design Question - Category Tree Hi Rodney, The reality is that I don't know what I am doing. I don't know how to force a category to have one parent. I don't know how to allow a category to have multiple parents. Thanks. Jim James D Homme, Usability Engineering Highmark Inc. james.homme@xxxxxxxxxxxx 412-544-1810 "It's more important for me to start to do the right thing than it is to wait until I think I can do it just right." "Rodney Haynie" <RodneyH@xxxxxxxx om> To Sent by: "programmingblind@xxxxxxxxxxxxx" programmingblind- <programmingblind@xxxxxxxxxxxxx> bounce@freelists. cc org Subject RE: Relational Database Design 09/12/2007 07:24 Question - Category Tree AM Please respond to programmingblind@ freelists.org 4 tables... Less duplicate data... That is true if you allow a category to have more than one parent. The key is to implement a scheme that you are comfortable with. -Rodney -----Original Message----- From: programmingblind-bounce@xxxxxxxxxxxxx [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of james.homme@xxxxxxxxxxxx Sent: Wednesday, September 12, 2007 7:04 AM To: programmingblind@xxxxxxxxxxxxx Subject: Re: Relational Database Design Question - Category Tree Hi, I think I should use four tables because there would be less duplicate data. Here is the summary of this thread as it was on the old list. Me: I want to depict a tree in a relational database. Here is what is going to happen. There will be a table that has items in it. The items can fall into categories. That means there will be a table of categories. An item can be in more than one category. I think this means that I need a third table. The third table will hold the number of an item from the items table and a number of a category from the categories table. I think I need another table that has a category number and a parent number. This would let me depict the categories inside other categories. Rodney: I would say you only need 3 tables: 1. Item 2. Category 3. ItemCategory I don't think you need another table because you can simply put the ParentCategoryID into the category table. You would join the category table to itself to get the parent category. Humberto: I think that you can handle the category and subcategory like eBay does. There is a field category_id and another field subcategory_of in the categories table. When the subcategory_of field is the same as the category_id field, you are at a top level category. Jim James D Homme, Usability Engineering Highmark Inc. james.homme@xxxxxxxxxxxx 412-544-1810 "It's more important for me to start to do the right thing than it is to wait until I think I can do it just right." __________ View the list's information and change your settings at //www.freelists.org/list/programmingblind __________ View the list's information and change your settings at //www.freelists.org/list/programmingblind __________ View the list's information and change your settings at //www.freelists.org/list/programmingblind __________ View the list's information and change your settings at //www.freelists.org/list/programmingblind __________ View the list's information and change your settings at //www.freelists.org/list/programmingblind __________ View the list's information and change your settings at //www.freelists.org/list/programmingblind __________ View the list's information and change your settings at //www.freelists.org/list/programmingblind __________ View the list's information and change your settings at //www.freelists.org/list/programmingblind __________ View the list's information and change your settings at //www.freelists.org/list/programmingblind