constraints on views

I found a schema with over a hundred constraints on views...not tables.

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View Constraints Oracle Database does not enforce view constraints. However,
you can enforce constraints on views through constraints on base tables.

You can specify only unique, primary key, and foreign key constraints on
views, and they are supported only in DISABLE NOVALIDATE mode. You cannot
define view constraints on attributes of an object column.
http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/clauses002.htm

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That passage isn't clear to me -- does it imply that constraints on views
can be created but never enforced?
How can that be useful?

If that is the case, I can't understand why someone would create a
constraint on a view instead of on the base tables.

No idea how these were created, maybe they were imported from Access or some
other environment.

Patrice.

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