[SQL] Cascade delete question

[Glenn MacGregor]

Hi All,
I am using a cascade delete on the following table:
vid    vname        parentname
1     [EMAIL PROTECTED]
2     [EMAIL PROTECTED]         [EMAIL PROTECTED]
3     [EMAIL PROTECTED]         [EMAIL PROTECTED]
4     [EMAIL PROTECTED]         [EMAIL PROTECTED]
5     [EMAIL PROTECTED]         [EMAIL PROTECTED]
So the delete cascade states if I am deleting a row whose vname matches 
the parentname delete those rows and it works fine.

I just changed the values of parentname (but the vname values stay the same)
vid    vname        parentname
1     [EMAIL PROTECTED]
2     [EMAIL PROTECTED]         n1
3     [EMAIL PROTECTED]         n1
4     [EMAIL PROTECTED]         n1
5     [EMAIL PROTECTED]         n3
Is there a way to do the same cascade delete with these values? I can 
select the correct info from vname in a query:

select substring(vname, from 0 for position('@' in vname)) from table1;
This works, so I tried to put that in the cascade but it failed.
Is there any way to accomplish this?
    Thanks
        Glenn MacGregor
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