"Jerry Stuckle" <jstucklex@attglobal.net> wrote in message
news:ePCdnbphcuUXnu_bnZ2dnUVZ_oPinZ2d@comcast.com. ..
> Jon Slaughter wrote:
>> "Gordon Burditt" <gordonb.j31n4@burditt.org> wrote in message
>> news:1373oig9j8ovpe4@corp.supernews.com...
>>>>>> Is there such a thing as ordered tables in sql or a simple way to
>>>>>> emulate
>>>>>> it? i.e., the order in the table matters and one can insert into
>>>>>> into
>>>>>> the table w.r.t to this order?
>>>>>>
>>>>>> I suppose I can have a column that sorta simulates the order but the
>>>>>> problem is that I don't see how I can simply insert a new row without
>>>>>> having to modify all others. If I could simply use the inherent order
>>>>>> of
>>>>>> the table then it would be much easier but then I think inserting
>>>>>> will be
>>>>>> very hard. I suppose I could have a unique ID for each one and I
>>>>>> think
>>>>>> that will work but not completely sure.
>>>>>>
>>>>>> Not sure if its possible to insert a row inbetween rows? But if I
>>>>>> could
>>>>>> and I could be sure that SQL would not modify the order then I think
>>>>>> I
>>>>>> could do it easily... else I end up having to have a field that
>>>>>> contains
>>>>>> relative information and I'd have to check every single row for it
>>>>>> which
>>>>>> is not what I'm going to do.
>>>>>>
>>>>>> Any ideas?
>>>>>>
>>>>>> Thanks,
>>>>>> Jon
>>>>> No. By definition, tables in RDB's are unordered. That's what the
>>>>> ORDER
>>>>> clause in the SELECT statement is for.
>>>>>
>>>> but how does it order it by?
>>> If your SQL specifies ORDER BY, that's how the output is ordered.
>>> (in the case of ties, the ordering between equal-order rows is not
>>> defined, but if you sort on a UNIQUE key, this won't be an issue).
>>> If your SQL does not specify ORDER BY, no matter what order you get
>>> for the output, you can't complain about it, since it's not wrong.
>>>
>>>> lexographical?
>>> Malevolent. The ordering will be such that it will seem to work fine
>>> until you demo it to the boss or a customer. See Murphy's Law.
>>>
>>>> I'm a little worried about how
>>>> I will set the id for each row so that when I order it it will give me
>>>> the
>>>> heirarchy. I don't think I can find a sufficient solution using that
>>>> unless
>>>> I can specify how it is to be ordered(without any non-portable sql
>>>> code).
>>> You don't have to order by numbers. You can use a string. Each
>>> item in a hierarchy can take the ID of its parent plus one additional
>>> character (or a fixed number of additional characters), which
>>> determines the ordering of its sub-topics. Suppose you have this
>>> (partial) outline for a paper:
>>>
>>> The Internet ()
>>>
>>> I. Viruses and Malware (1)
>>> A. Microsoft Windows (1A)
>>> B. Internet Explorer (1B)
>>> II. Criminals on the Internet (2)
>>> A. Spammers (2A)
>>> B. Predators (2B)
>>> 1. Cops pretending to be kids (2B1)
>>> 2. Chris Hansen (2B2)
>>> 3. Cops pretending to be FBI (2B3)
>>> C. Fraudsters (2C)
>>> 1. Phishing attacks (2C1)
>>> 2. Phalse advertising (2C2)
>>> III. Copyright Infringement (3)
>>> A. Stolen Music (3A)
>>> B. Stolen Movies (3B)
>>> C. Stolen Software (3C)
>>>
>>> If it's an unordered hierarchy, new items can be added at the end
>>> under the parent, for example, "Stolen Pictures" probably gets (3D).
>>> If you insist that it has to go between "Stolen Music" and "Stolen
>>> Movies", it gets (3B), and you only have to renumber "Stolen Movies"
>>> and "Stolen Software".
>>>
>>
>> I don't see how its that efficient... if I have 100's of levels with
>> 100's of children then using just letters can start to waste space very
>> quickly.
>>
>> if I use each char as a full byte(0..255) then how do they get compared?
>>
>>
>> I think I can use a decimal if I encode it properly to represent the
>> level and it should work fine with the order by.
>>
>> I can't see how using a full char(0..255) and concatinating them to form
>> an id will be processed by order correctly and just using letters(0..25 I
>> suppose since its probably not case sensitive) is about 10 times more
>> space(and because I need a larger number of "levels" it will quickly add
>> up to).
>>
>> Jon
>
> The question arises - what exactly are you trying to do? 100's of levels?
> 100's of children?
>

100's of nodes. its about nesting or if you prefer, tree's.