20.5 Not All Views with Objects Are Object Views

Chapter 20
Object Views

 

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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.