Re: Updatable views

Probably in vain but I will give you answers.

On Wed, 7 Dec 2005 11:08:57 +0200, "x" <x_at_not-exists.org> wrote:

>
>"Rick Elbers" <rick.elbers_at_chello.nl> wrote in message
>news:3189p1dlv9qpofqai5nq8v32keao7amiph_at_4ax.com...
>> Dear database experts,
>
>> Can somebody enumerate the problems with an updatable view for me ?
>> With an updatebleview:= joined set of related tables and relations
>> from which rows can be updated, inserted and deleted like you
>> can in a simple table or master-detail relation.
>
>What is an updatable view in your view ?

Defined that above. See above

>What do you mean by joined set of related tables and relations ?

A list of tables which are joined( flattened if you want) on their related identifiers( keys if you want). In fact your regular join

>Maybe you mean just a set of tables ?

Yes, I think so

>What do you mean by related ?

With a foreign key-primary key relation

>There is any constraint definition ?

Could be. Couldnt be. Should both be possible

>Who is enforcing the constraints ? The DBMS or the application ?

the DBMS.

>Who is doing the translation of the update requests ? The application or the
>DBMS ?
Thats the point. As much as possible the class UpdatableView.

>How you deal with the errors ?

That too is responsibility of UpdatableView

>Are we talking about SQL DBMS or something else ?

Yes we are talking about sql server to be precise( although I doubt it matters)

>etc. etc. etc.

Etc etc trivial answers

>
>> My first try is to find hierarchy in de database by finding the
>> absolute parents assigning them level 0. Parents of my table are
>> considered those relations in which my foreign key doesnt allow
>> DBNull.
>
>What if do not find any parent this way ?

Then you are safe to insert/update anything in that table

>And what is the purpose of building the hierarchy ?

See above. Do you really understand the problem or not ?
>
>> Then from there on proceed to give every table that has no parents but
>> level 0 parents a level 1 etc.
>>
>> Problems seem to be autojoins and multiple relations between tables.
>> Those problem can be solved to use every table only once in the scan.
>>
>> So the first question is: will this way of hierarchising the
>> relational db always valid ?
>
>> Then secondly given the hierarchy what problems remain when we talk
>> about insert/update/delete and all kinds of combinations of those ?
>
>Gee! Let me think. The problems are ... what is the problem again ?
>

Funny guy. The problem is the database. How to get rid of its messing with good OO code.

>> Regards and tx for answering,
>>
>> Rick Elbers
>>
>>
>>
>>
>>
>

Rick Received on Wed Dec 07 2005 - 21:48:17 CET