Distributed Database Systems, 1st Edition by Chhanda Ray

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Distributed Database Systems

Example 12.3

The view V1 in example 12.1 is updatable, whereas the view V2 in example 12.2 is non-updatable

because the query expression for creating view V2 involves one base relation and one view. The

insertion of a new tuple ⬍D. Jones, Manager, 40⬎ into V1 can be propagated to the base relation

Employee without any ambiguity. The following view is a non-updatable view.

Create view V3 as select max(salary) from Employee

The above view V3 contains an aggregate function MAX, thus, it is non-updatable. Similarly, the

following view V4 is also non-updatable.

Create view V4 as select * from V2

The above view is non-updatable ...