Celko also discusses them in SQL For Smarties.
Baron
Peter Brawley wrote:
> Matt
>
> >I'd like to store paths to specific destinations...
>
> See
> -- Tropashko's 'materialized modell' eg
> http://www.dbazine.com/oracle/or-articles/tropashko4
> -- the airports example at
> http://www.artfulsoftware.com/mysqlbook/sampler/mysqled1ch20.html
>
> PB
>
> -----
>
> Matt Juszczak wrote:
>> Hi all,
>>
>> I've got a table such as the following:
>>
>> id1 char
>> id2 char
>>
>> sample data looks like this:
>>
>> id1 id2
>> 1 3
>> 2 4
>> 3 5
>> 5 6
>> 6 8
>>
>> And of course another table has something like:
>>
>> id info1 info2 info3
>> 1 blah blah blah
>> 2 blah blah blah
>>
>> I'd like to store paths to specific destinations...
>>
>> In other words, the path from 1 to 8 is:
>>
>> 1,3,5,6,8
>>
>> I was thinking of creating a table called relationships
>>
>> start end path
>> 1 8 {3,5,6}
>>
>> This would allow me to easily display the path if I know the start and
>> end, but what it doesn't allow me to do is reuse the data.
>>
>> IE: say that I calculate the path from 1 to 8 as 1,3,5,6,8, and then I
>> want to know the path from 3 to 6. even though this is already
>> calculated, I have to recalculate it as another row... hence
>>
>> start end path
>> 1 8 {3,5,6}
>> 3 6 {5}
>>
>> I considered making another table, called hops, such as:
>>
>> start end relationshipID
>> 1 8 1
>>
>>
>> table hops:
>> relationshipID start end
>> 1 1 3
>> 1 3 5
>> 1 5 6
>> 1 6 8
>>
>> Then I could almost "reuse" those hops somehow.... but not sure.
>>
>> Can anyone recommend a good way to store this data?
>>
>> Thanks!
>>
>> -Matt
>>
>
--
Baron Schwartz
http://www.xaprb.com/
