Обсуждение: Cascade delete question

Hi All,

Sorry if this is a double post.

Here is an example of my table which works

vid    vname        parentname
1    n1@test.com
2    n2@test.com    n1@test.com
3    n3@test.com    n1@test.com
4    n4@test.com    n1@test.com
5    n5@test.com    n3@test.com

So my simple cascade on delete states that if I delete a row whose vname
matches the parentname of any other delete those rows.

No problem this works great!

Now I have changed my data to

vid    vname        parentname
1    n1@test.com
2    n2@test.com    n1
3    n3@test.com    n1
4    n4@test.com    n1
5    n5@test.com    n3

Notice the parentname is a substring of the vname. I can get that
substring from a select query

select (substring(vname from 0 for position('@' in vname)) from table1

This query returns
vname
------
n1
n2
n3
n4
n5

Can I change my delete cascade constraint to do this substring query
instead of an exact match?

Is there anyway to accomplish what I need to do?

    Thanks

        Glenn MacGregor

On Thu, Apr 22, 2004 at 16:46:31 -0400,
  Glenn MacGregor <gtm@highstreetnetworks.com> wrote:
>
> No problem this works great!
>
> Now I have changed my data to
>
> vid    vname        parentname
> 1    n1@test.com
> 2    n2@test.com    n1
> 3    n3@test.com    n1
> 4    n4@test.com    n1
> 5    n5@test.com    n3
>
> Can I change my delete cascade constraint to do this substring query
> instead of an exact match?

No.

> Is there anyway to accomplish what I need to do?

If the local part of the email address is a candidate key, separate it
from the domain name and make it the primary key.