一个类的父类和实现的所有接口都称为这个类的超类型(Supertype)，而这个类称为其超类型的子类型(Subtype) 子类型的对象引用可以造型成其任意超类型(类或接口)的对象引用，这就是对象的多态性
基于210个网页-相关网页
了解如何创建实体超类型、子类型和相关服务。
Understand how to create an entity supertype, subtypes, and associated services to allow the processing of each.
作为一个应用于所有几何类型的函数，它实际上是超类型的一个方法。
ST_Geometry, which is the supertype to all geometry types; as a function that applies to all geometry types, it is properly a method of the supertype.
子类型所继承的属性来自哪个类型，该类型就被认为是这个子类型的超类型。
The type from which a subtype inherits attributes is known as its supertype.
应用推荐