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Re: SQL to combine columns

Posted by Ed Murphy on 03/12/07 16:55

yuri wrote:

>> Yes it is brought up all the time because people will not bother to
>> read even one book on RDBMS, so they keep asking this kind of thing
>> over and over. Please post DDL, so that people do not have to guess
>> what the keys, constraints, Declarative Referential Integrity, data
>> types, etc. in your schema are. Let's start by doing what you should
>> have done for us:
>
> Oh, I'm sorry about that. I failed to get a copy of the CELKO SQL
> posting etiquette. Could you please point me in the right direction?
> Sarcasm aside, I will do this in the future. Thanks.

He's pretty much always like that. You get used to it after a while.

>> Why do you wish to destroy First Normal Form (1NF) with a concatenated
>> list structure? It is the foundation of RDBMS, after all. See why I
>> say you never read a book on RDBMS.
>
> You're right I should have went out and bought a book on RDBMS. I mean
> who would ever think about asking a question on the internet was
> possible. I mean everybody should shut down all forums and rely on tech
> manuals because they are always so well written and contain every piece
> of knowledge on the planet about the subject, including all the hidden
> tips and tricks. Questions will be a thing of the past. Just grab a
> book and your answer will be there. Did you get criticized in class
> when you had a question about something? Did the teacher yell at you,
> tell you to read the book and never answer the question?

This is not a class. It's reasonable to expect people to do at least
a bit of reading on their own first.

>> Why did you think that an owner is an attribute of a dog? It is a
>> relationship! It might have attributes of its own, like license
>> numbers, issue date, etc. but let's ignore that.
>
> I think a dog belongs to an owner. Can an owner have more than 1 dog?
> Hmmm.... I think so in this example. Yes, creating a seperate table in

But can a dog have more than one owner? If so, then the relationship
should indeed be moved into a third table.

This (among many other issues) is the sort of thing that questioners
tend to gloss over, not because they haven't thought about it, but
because the answer is obvious to them (whereas it is not obvious to
the rest of us). Politeness issues aside, I think it's a net gain
for such issues to be pointed out pre-emptively.

 

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