Re: SQL, related records (quotes)

mAsterdam wrote:
> Jan Hidders wrote:
>

>> Stefan Rybacki wrote:
>>
>>> timpea_at_gmail.com wrote:
>>>
>>>> Hi,
>>>>
>>>> I have a website that users can request quotes, and a user may also
>>>> make a new quote that links to a previous quote.
>>>>
>>>> QuoteNo    PreviousQuoteNo
>>>>      1
>>>>      2
>>>>      3                     1
>>>>      4                     3
>>>>      5                     4
>>>>
>>>> If i request quoteNo 3 i want to have a list of all the related quotes.
>>>>
>>>>
>>>> RelQuote
>>>>      1
>>>>      3
>>>>      4
>>>>      5
>>>>
>>>> Is this possible with a SQL statement? or would i be best doing a loop
>>>> in asp and many requests?
>>>> Thanks Tim Pearson
>>>>
>>>
>>> Try the nested sets model.
>>
>>
>> Are you sure the relation describes always a tree?

That is true but these are inconsitent states. Its clear that you can create those table values by hand but think about it in algorithmic way:

you want to create a quote with QuoteNo=3 so how can you say its parent is QuoteNo=6 since there is no quote with this number. Ok somebody can say what if QuoteNo=6 is already existing. Ok we go from there so how could this quote (6) have known from QuoteNo=3? since we are currently creating it?

Same for the second example.

Regards
Stefan Received on Fri Jun 24 2005 - 23:46:42 CEST