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20.5 Not All Views with Objects Are Object Views

With the Oracle objects option installed, there are other interesting possibilities for views which do not necessarily qualify as "object views." For example, you can create a view that has an object as a column:

CREATE TABLE requisition (
   req_no INTEGER,
   image_id NUMBER
);

CREATE VIEW requisition_v
AS
   SELECT r.req_no, VALUE(i) image
     FROM requisition r,
          images_v i
    WHERE r.image_id = i.image_id;

The requisition view now has two columns: one for the req_no, of type INTEGER; and one for the image, of type Image_t.

You can combine many object features into an object view. For instance, you can define an object view that includes a column that contains a collection of objects. Just because the possibilities seem endless, though, there is no excuse to get carried away; objects should be restricted to "natural" representations of data; they shouldn't serve merely as the basis of intellectual calisthenics for the programmer.


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