Re: How to represent a tree-structure in a relational database

On Wed, Dec 13, 2000 at 11:38:18AM -0800, Stuart Statman wrote:
[ . . . ]
> I would suggest, instead, to create a table that represents your hierarchy
> without adding columns. For example :
>
> create table Category (
> CategoryID int4 not null primary key,
> ParentCategoryID int4 not null REFERENCES Category (CategoryID),
> CategoryName varchar(100)
> );
>
> Add a CategoryID with an FK reference to this table, and your work is done.
>
> Then adding, inserting, removing, or moving layers in the hierarchy becomes
> quite simple. This also preserves hierarchical integrity, where subcategory
> a of subcategory b will also remain a subcategory of category c if
> subcategory b is a subcategory of subcategory c, where I'm not sure your
> model will preserve or guarantee that. (Does that sentence deserve a prize?)

Cool. That looks like my solution. I had actually seen it someplace
before, but didn't make the connection with my problem.

Ta, Frank