Re: Delete cascade?
Re: Delete cascade?
- Subject: Re: Delete cascade?
- From: Ian Joyner <email@hidden>
- Date: Wed, 21 Mar 2007 10:47:51 +1100
Thanks Chuck for responding to my persistent questioning - I knew
there was some interesting stuff here. And thanks to Ray explaining
the philosophy of why EOF might not always have optimal SQL – that's
fine with me.
On 21/03/2007, at 4:43 AM, Chuck Hill wrote:
I am pretty sure that is not what it is doing (assuming that I
understand your meaning). I am pretty sure this is what it does
after you call save changes (totally from memory, may be slightly
out of order):
Thanks for the great list.
That might be acceptable in some situations, but not in all. EOF
pointedly deletes what it knows about and nothing else. If there
are other records, the DB will return an error when the
transaction is committed. This will inform the application which
can then take appropriate action.
But I still think that is the meaning of setting 'cascade' rather
than 'deny'. I think this is introducing a shade of grey in between.
I can see your point.
I think for the grey in between you'd use 'no action' and handle it
yourself – but I don't want to consider such complex rules since
normally cascade, nullify, or deny will handle most situations.
Thanks, it's an interesting topic, I think I'll run back to the
Chris Date and Jim Gray now.
I'm glad that someone else thinks it is an interesting topic. I
was starting to feel like a geek. :-P As for the Chris Date,
forget the SQL. The database is just an artifact of
implementation. Objects are where its at.
Hmmm, geeks generally don't make any sense. Don't worry about Christ
Date - he doesn't like SQL either (mainly because it is a bad
implementation of good RDB concepts (relational algebra), for
instance SELECT implements the two orthogonal operators of 'select'
and 'project'). I don't even think Codd likes SQL. So I have never
written any SQL with EOF, and don't intend to. Date and Gray are just
good books on the principles of DBs and transaction processing.
I'd agree that part of the beauty of EOF is its object-relational
mapping allowing you to build flexible and previously unthought of
apps (D2W) on top of relational DBs, rather than having a fixed set
of relationships between entities as you do with hierarchical,
network, or OO DBs, which preclude flexibility.
Ian
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