Re: [Gnumed-devel] data integrity question

[Karsten Hilbert]

> If an org gets deleted, should its comm_channell entries also get 
> deleted from the database,
One would tend to think that identical comm channels can be
linked from several orgs/identities. However, this is not the
case, or rather, one needs to set up a policy what to do when
a comm channel is to be changed. The options are:

1) 
On insert create new.
On update update linked row.
On delete delete linked row.

2)
On insert link to existing.
On update copy-on-update and updated newly linked row.
On delete delete link but leave alone linked row.

It seems cleaner to use option 1. However, there's one
problem: PG does not support multi-table uniqueness (as would
be needed to make sure that any comm_channel is linked from
EITHER an org OR an identity. And from *one* of either, for
that matter.

However, if linked from more an org and an identity the delete
will fail due to foreign key references still in place.

I have added a few on update/delete statements to the
lnk_*2comm_channel tables, too.

Karsten
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