What is inheritance in SQL?

What is inheritance in SQL?

SQL object inheritance is based on a family tree of object types that forms a type hierarchy. The type hierarchy consists of a parent object type, called a supertype, and one or more levels of child object types, called subtypes, which are derived from the parent.

What is SQL subtype?

A subtype is a definition of a type based on a built-in type. Subtypes provide a layer of abstraction between variables and parameters and the data types that they use. This layer allows you to concentrate any changes to the data types in one location.


In PL/SQL, object-oriented programming is based on object types. They let you model real-world objects, separate interfaces and implementation details, and store object-oriented data persistently in the database.

How do I declare an object in SQL?

Using object types in a PL/SQL block, subprogram, or package is a two-step process.

  1. You must define object types using the SQL statement CREATE TYPE , in SQL*Plus or other similar programs.
  2. In PL/SQL, you then declare a variable whose data type is the user-defined type or ADT that you just defined.

Does SQL Server support inheritance?

Using “sub-type” tables is a simple way to implement table inheritance in SQL Server. …

What is subtype and supertype?

A supertype is a generic entity type that has a relationship with one or more subtypes. A subtype is a sub-grouping of the entities in an entity type that is meaningful to the organization and that shares common attributes or relationships distinct from other subgroups. Subtypes inherit all supertype attributes.

What is an example of subtype?

Subtypes are a subset of features in a feature class, or objects in a table, that share the same attributes. They are used as a method to categorize your data. For example, the streets in a city streets feature class could be categorized into three subtypes: local streets, collector streets, and arterial streets.

What is PL SQL table?

Objects of type TABLE are called PL/SQL tables, which are modeled as (but not the same as) database tables. Like an array, a PL/SQL table is an ordered collection of elements of the same type. Each element has a unique index number that determines its position in the ordered collection.

What are the Plsql objects?

PL/SQL allows defining an object type, which helps in designing object-oriented database in Oracle. An object type allows you to create composite types. Using objects allow you to implement real world objects with specific structure of data and methods for operating it. Objects have attributes and methods.

What are the examples of RDBMS?

Examples of the most popular RDBMS are MYSQL, Oracle, IBM DB2, and Microsoft SQL Server database.

What is an object table?

Object tables are tables based upon user defined data types so in all cases, in the demos below, you will see tables based on object types defined by Oracle as part of the database deliverable or created by the developer or DBA.

What does it mean when an object type is not instantiateable?

You can mark an object type as NOT INSTANTIABLE , which prevents objects of that type from being created. You might want to mark an object type as NOT INSTANTIABLE when you want to use that type only as a supertype.

How do I Mark an object type as not instantiable?

You might want to mark an object type as NOT INSTANTIABLE when you want to use that type only as a supertype. For example, you could create a type to represent vehicles and use it as a supertype for another type to represent cars and motorcycles. The following statement creates a type named vehicle_typ , which is marked as NOT INSTANTIABLE :

What is inheritance in SQL Server?

2.3.1 About Inheritance in SQL Object Types Inheritance is the mechanism that connects subtypes in a hierarchy to their supertypes. Subtypes automatically inherit the attributes and methods of their parent type. Also, the inheritance link remains alive.

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