Re: parent/child relationship in the same table.

In article <6768b874.0111190856.38dff697_at_posting.google.com>, Jason Diamond says...
>
>> before we are getting into this lets return to your question. Is it just plain
>> hierarchy that is surfacing once in a while in this thread? For hierarchy you
>> have plenty of solutions:
>>
>> 1. Recursive SQL (SQL 99 standard, implemented in DB2)
>> 2. Oracle "connect by"
>> 3. Incremental evaluation of transitive closure.
>
>It certainly is a hierarchy problem so probably is a FAQ.

Every 3 mo or so a question on hierarchy surfaces in this group, but AFAIK there is no FAQ:-(

>I'm using SQL Server so solutions 1 and 2 are automatically ruled out.
>Do you have any pointers on number 3?

Here is incomplete classification:
1. Incremental evaluation systems for general graphs. The idea behind is that whenever you add a link <a,b> into a path like this:

x---->a b---->y

you also need to add links <x,b>, <a,y>, <x,y> into the adjucency relation. Obxiously this must be done for every couple (x,y) of nodes in the graph. Almost any paper on incremental evaluation mentiones that method -- just pull out Google.

2. Methods for hierarchy. "Yet another hierarchy model" thread on comp.databases.theory shows how many different techniques are there.

>By the way, is there a FAQ document for the group? A quick search on
>Google didn't find one.
Received on Mon Nov 19 2001 - 18:54:32 CET