Database Program Translation - Information Systems Reengineering, Integration and Normalization - page 212

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Step 3. Delete the to-be-deleted object.
We can then delete the to-be-deleted object from its class C k as:

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Note: ALL is needed to delete all the subclasses' objects only if deleting a super-
class object.

5.10.1 Relational Operation Update

Suppose we want to replace the value of an attribute v k from value V(v k1 ) to V(v k2 )
in the relation R k (which maps to class C k ). Basically, we consider two cases. In the
first case, v k is not a foreign key. It corresponds to an attribute in the corresponding
object, and thus we need an update statement of OSQL to perform the replacement.
In the second case, v k is a foreign key. Replacing a value in this case involves
changing the aggregate attributes of its composite as shown below:
Step 1. Locate the to-be-updated object.
We can map a to-be-updated tuple in relation R k to a corresponding to-be-updat-
ed object in class C k as:

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Step 2 (optional). Update aggregate attribute of composite objects containing to-be-
updated object.
If the to-be-updated attribute is an aggregate attribute (P c or P p ), we can locate
the aggregate attribute P c or P p in the to-be-updated object, and then delete (the