Re: [sqlite] Best method to create a database with a tree structure?
On Mon, Jan 19, 2004 at 06:52:41AM +0800, John Scott wrote:
>
> Hello folks,
>
> I am thinking of to create a database with a tree structure.
> ...
Hi,
A very interesting way is described in the excellent book "Advanced
SQL" by Joe Celko: basically, a tree can be viewed as a set of
(sub-)sets. The root is the bigger set because it contains all the
others.
Imagine you have a tree of person names:
Foo
|
| |
aaa bbb
|
ccc
A node is a record of the following table :
CREATE TABLE Person (
name char(3),
left integer,
right integer
);
And the above tree can be described with these records :
NAME LEFT RIGHT
Foo 1 8
aaa 2 5
ccc 3 4
bbb 6 7
I hope this example will give you the general idea. I'm sure you
can find much more information about this method on Google.
Regards,
Stephane.
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Re: [sqlite] Best method to create a database with a tree structure?
Hi Martin, You are talking about standard Parent/Child relationships here but because you have unlimited number of entries you fold it into one table and have a Parent_ID column. So if you have your required details as being these columns Name SomethingElse Then a standard table might be Name_ID Name Somethingelse adding the parent id column would be Name_ID Name Somethingelse Parent_ID or Create Table TableName ( Name_ID INTERPER PRIMARYKEY , Name , Somethingelse , Parent_ID ) Now all you need to do is fill in the details , PARENT_ID = 0 means it has no parents (or leave it NULL if you want) When you retrieve the rows you always do select * from Tablename where Parent_ID = 2 (or what ever) regards Greg O - Original Message - From: John Scott To: [EMAIL PROTECTED] Sent: Monday, January 19, 2004 9:52 AM Subject: [sqlite] Best method to create a database with a tree structure? Hello folks, I am thinking of to create a database with a tree structure. BUt it seems to be a hard work. I would like to have a tree structure embbeded into the database like: Root folder which contains two other folders "books" and "music". If a click on books, only the entries in the database which belong to the folder bools under root should be displayed. Does someone have a good idea?? Thanks, Martin - 每天都 Yahoo!奇摩 海的顏色、風的氣息、愛你的溫度，盡在信紙底圖 信紙底圖
[sqlite] Best method to create a database with a tree structure?
Hello folks, I am thinking of to create a database with a tree structure. BUt it seems to be a hard work. I would like to have a tree structure embbeded into the database like: Root folder which contains two other folders "books" and "music". If a click on books, only the entries in the database which belong to the folder bools under root should be displayed. Does someone have a good idea?? Thanks, Martin - 每天都 Yahoo!奇摩 海的顏色、風的氣息、愛你的溫度，盡在信紙底圖 信紙底圖
