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From Libor Jelinek <ljeli...@virtage.com>
Subject Re: How to drop two interrelated tables at the same time?
Date Fri, 10 Feb 2012 20:09:01 GMT
I am sorry I was corrected by friend of mine that it's Aristotle's idea,
not Columbus's (also known as "chicken or the egg") :-)

Thanks
Libor

2012/2/10 Libor Jelinek <ljelinek@virtage.com>

> Right, John. Because these two tables reference each other with FK
> constraints thus one column must allow null. Then it's application logic's
> responsibility to ensure that immediately when referenced row from second
> table is created it is set in first table (i.e. not leaving it null).
>
> By the way are there some methodologies in response to this "Columbus's
> egg" problem?
>
> Thank you for your helpful responses!
> Libor
>
> 2012/2/10 John English <john.foreign@gmail.com>
>
>> On 10/02/2012 02:22, Bergquist, Brett wrote:
>>
>>> Use
>>>
>>> alter table business_objects drop constraint fk_created_by;;
>>> alter table users drop constraint fk_boid;
>>> drop table business objects;
>>> drop table users;
>>>
>>> Basically reverse what you did to create the tables.
>>>
>>> Brett
>>>
>>
>> As a matter of interest, how would you ever insert data into these two
>> tables? Inserting into either one would violate the FK constraint in
>> the other, unless the FK allowed nulls -- in which case you do an insert
>> with a null key into one table, an insert with non-null into the other,
>> and then an update of the first table's FK. Or am I missing something?
>>
>> ------------------------------**------------------------------**
>> ------------
>>  John English | My old University of Brighton home page is still here:
>>              | http://www.cem.brighton.ac.uk/**staff/je/<http://www.cem.brighton.ac.uk/staff/je/>
>> ------------------------------**------------------------------**
>> ------------
>>
>
>

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