Example data type hierarchy
Assume you are designing three data types: MyPoint, MyBox,
and MyCircle. Because they are all two-dimensional spatial data types,
a supertype called MyShape could also be defined. This type hierarchy
is described in the following figure.
Figure 1. Data type hierarchy
Using SQL, create casts between the three subtypes (MyPoint, MyBox, and MyCircle) and the supertype, MyShape.