Re: SQL, related records (quotes)

mAsterdam wrote:
> Stefan Rybacki wrote:
>

>> mAsterdam wrote:
>>
>>> Jan Hidders wrote:
>>>
>>>> Stefan Rybacki wrote:
>>>>
>>>>> timpea_at_gmail.com wrote:
>>>>>
>>>>>> 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?
>>>>>
>>>>>
>>>>> Try the nested sets model.
>>>>
>>>>
>>>> Are you sure the relation describes always a tree?
>>>
>>>
>>> Values like
>>> QuoteNo    PreviousQuoteNo
>>>       3           6
>>>       6           3
>>>
>>> or just
>>> QuoteNo    PreviousQuoteNo
>>>       3           3
>>>
>>> are possible, so no tree. The columnnames suggest the OP does not
>>> want this to happen. They don't help to prevent these loops though.
>>
>>
>>
>>
>> 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?

Oops - still not good enough. Received on Sat Jun 25 2005 - 00:21:29 CEST