Re: delete from a view

From: Howard J. Rogers <hjr_at_dizwell.com>
Date: Thu, 29 Apr 2004 19:18:24 +1000
Message-ID: <4090c859$0$20662$afc38c87@news.optusnet.com.au>

Frederic Houbie wrote:

> On Wed, 28 Apr 2004 21:06:43 +0000, Brian Peasland wrote:
>
>

>>>In fact, I have a Oracle Type T1 and several type that inherit T1. For
>>>each child type, I have an oracle table of that type.
>>>My view is a view that return T1 object and is the union of all the table
>>>that are childs of t1, so, I'm sure that I have no duplicate row and key
>>>(which are uuid so unique in the world) are unique. That's
>>>the reason why I thought I could delete a row from that view.
>>
>>But you can't guarantee uniqueness between the base tables involved in
>>the UNION ALL. What mechanism does the database have to guarantee that a
>>record in TABLE1 is not also present in TABLE2? There isn't one
>>(natively). But all of this makes no difference since you can't delete
>>from a UNION ALL view.
>>
>>Cheers,
>>Brian

>
> ID primary key are generated by my java application. It uses Global id
> generation like urn:uuid:6ef7f826-2837-457a-bbf1-b963a9c85cd5 which use
> MAC address of network card to generate the key. So, i'm sure that I do
> not have two similar key in the database.
>
> Fred
>

You've missed Brian's point. *You* know the things are unique, but how is the *database* supposed to know that? In the general case, it cannot possibly. Hence the rule: no deleting from a union all view.

Regards
HJR Received on Thu Apr 29 2004 - 04:18:24 CDT