l14 l15 oo dbms

Rushdi Shams, Dept of CSE, KUET

Database Database SystemsSystems

Object Oriented Database Object Oriented Database Management SystemsManagement Systems

Version 1.0Version 1.0


Object- TheoryObject- Theory

An object is a package of data and An object is a package of data and procedures.procedures.

Data is contained in attributes of an Data is contained in attributes of an objectobject

Procedures are defined in methods Procedures are defined in methods of an objectof an object


Object- TheoryObject- TheoryConcept of ClassConcept of Class


Objects- TheoryObjects- TheoryConcepts of ObjectsConcepts of Objects


Object Types in OracleObject Types in OracleConcept of ClassConcept of Class


Objects in OracleObjects in Oracle

When you create a variable of an When you create a variable of an object type, you create an instance object type, you create an instance of the type and the result is an of the type and the result is an objectobject

An object has the attributes and An object has the attributes and methods defined for its typemethods defined for its type

an object instance is a concrete an object instance is a concrete thing, you can assign values to its thing, you can assign values to its attributes and call its methodsattributes and call its methods


Objects in OracleObjects in Oracle

rushdirushdi person_typ;person_typ;

will create an object named rushdi of will create an object named rushdi of type person_typ.type person_typ.


Question at the stageQuestion at the stage

How the property ENCAPSULATION How the property ENCAPSULATION reflects in OODM?reflects in OODM?

What is the difference between What is the difference between object type and object in Oracle?object type and object in Oracle?

What is the relation between What is the relation between Oracle’s object type and OOP’s Oracle’s object type and OOP’s class?class?


Object Type is a Data Object Type is a Data Type!Type!

Defining an object type does not Defining an object type does not allocate any storageallocate any storage

After they are defined, object types After they are defined, object types can be used in SQL statements in can be used in SQL statements in most of the same places you can use most of the same places you can use types like NUMBER or VARCHAR2types like NUMBER or VARCHAR2


Object Type is a Data Object Type is a Data Type!Type!


Question at the stageQuestion at the stage

““An object type is a data type”- An object type is a data type”- justify the answer.justify the answer.


Object Methods in OracleObject Methods in Oracle

Methods are functions or procedures Methods are functions or procedures that you can declare in an object type that you can declare in an object type definition to implement behavior that definition to implement behavior that you want objects of that type to you want objects of that type to performperform

The general kinds of methods that can The general kinds of methods that can be declared in a type definition are:be declared in a type definition are:

1.1. MemberMember2.2. StaticStatic3.3. ConstructorConstructor


Member MethodsMember Methods

Member methods are the means by which Member methods are the means by which an application gains access to an object an application gains access to an object instance's data instance's data

You define a member method in the object You define a member method in the object type for each operation that you want an type for each operation that you want an object of that type to be able to perform object of that type to be able to perform


Static MethodsStatic Methods

Static methods are invoked on the Static methods are invoked on the object type, not its instances object type, not its instances

You use a static method for You use a static method for operations that are global to the operations that are global to the type and do not need to reference type and do not need to reference the data of a particular object the data of a particular object instance instance

A static method has no SELF A static method has no SELF parameter parameter


Static MethodsStatic Methods

You invoke a static method by using You invoke a static method by using the dot notation to qualify the the dot notation to qualify the method call with the name of the method call with the name of the object type, such as:object type, such as:

type_name.method()type_name.method()


Constructor MethodsConstructor Methods

Every object type has a constructor method Every object type has a constructor method implicitly defined for it by the system implicitly defined for it by the system

A constructor method is a function that A constructor method is a function that returns a new instance of the user-defined returns a new instance of the user-defined type and sets up the values of its attributes type and sets up the values of its attributes


Questions at the StageQuestions at the Stage

What are the three methods that can What are the three methods that can be declared in object type definition?be declared in object type definition?

What is the difference between What is the difference between static method and member method?static method and member method?

What is the speciality about What is the speciality about constructor method?constructor method?


Inheritance- TheoryInheritance- Theory

A type hierarchy is a sort of family A type hierarchy is a sort of family tree of object types tree of object types

It consists of a parent base type, It consists of a parent base type, called a super type called a super type

one or more levels of child object one or more levels of child object types, called subtypes types, called subtypes

Child object types are derived from Child object types are derived from parent object classparent object class



A subtype becomes a specialized A subtype becomes a specialized version of the parent type by adding version of the parent type by adding new attributes and methods to the new attributes and methods to the set inherited from the parent or by set inherited from the parent or by redefining methods it inherits redefining methods it inherits

Redefining an inherited methods Redefining an inherited methods gives a subtype its own way of gives a subtype its own way of executing the method executing the method


PolymorphismPolymorphism

Add to this that an object instance of Add to this that an object instance of a subtype can generally be a subtype can generally be substituted for an object instance of substituted for an object instance of any of its supertypes in code, and any of its supertypes in code, and you have polymorphism you have polymorphism


Final & Not Final- TypesFinal & Not Final- Types

The definition of an object type The definition of an object type determines whether subtypes can be determines whether subtypes can be derived from that type derived from that type

To permit subtypes, the object type must To permit subtypes, the object type must be defined as not final be defined as not final


Final & Not Final- TypesFinal & Not Final- Types

By default, an object type is declared as By default, an object type is declared as final and subtypes cannot be derived from final and subtypes cannot be derived from it it

You can change a final type to a not final You can change a final type to a not final type and vice versa with an ALTER TYPE type and vice versa with an ALTER TYPE statementstatement

You can alter a type from NOT FINAL to You can alter a type from NOT FINAL to FINAL only if the target type has no FINAL only if the target type has no subtypes subtypes


Final & Not Final- Final & Not Final- MethodsMethods

Methods can also be declared to be Methods can also be declared to be final or not final final or not final

If a method is declared to be final, If a method is declared to be final, subtypes cannot subtypes cannot overrideoverride it by it by providing their own implementation providing their own implementation

Unlike types, methods are not final Unlike types, methods are not final by default and must be explicitly by default and must be explicitly declared to be final declared to be final


Final & Not Final- Final & Not Final- MethodsMethods


Inheritance- OracleInheritance- OracleCreating SubtypeCreating Subtype


Inheritance- OracleInheritance- OracleCreating Subtype of Creating Subtype of

subtypesubtype



What are the mechanisms Oracle What are the mechanisms Oracle use to reflect the INHERITANCE of use to reflect the INHERITANCE of object oriented architecture?object oriented architecture?

What is the significance of FINAL What is the significance of FINAL and NOT FINAL?and NOT FINAL?

What is the difference of FINAL and What is the difference of FINAL and NOT FINAL in case of object types NOT FINAL in case of object types and methods?and methods?


Method Overriding- Method Overriding- TheoryTheory

An method is said overriding if the An method is said overriding if the method name is same for all the method name is same for all the objects but the objects define how objects but the objects define how the method works according to their the method works according to their convenience.convenience.


Method Overriding- Method Overriding- OracleOracle


Taking you to the Reality Taking you to the Reality


Taking you to the Reality Taking you to the Reality

You can call the show() function for the You can call the show() function for the supertype and subtypes in the table with supertype and subtypes in the table with the following the following


& The output & The output


Method Overloading- Method Overloading- TheoryTheory

Giving a type multiple methods with Giving a type multiple methods with the same name is called method the same name is called method overloading overloading


Method Overloading- Method Overloading- OracleOracle



What are the difference between What are the difference between method overloading and method method overloading and method overriding?overriding?

How Oracle implements method How Oracle implements method overriding?overriding?

How Oracle implements method How Oracle implements method overloading?overloading?


Map MethodsMap Methods

A map method is an optional kind of A map method is an optional kind of method method

provides a basis for comparing objects provides a basis for comparing objects by mapping object instances to one of by mapping object instances to one of the scalar types DATE, NUMBER, the scalar types DATE, NUMBER, VARCHAR2 or to an ANSI SQL type VARCHAR2 or to an ANSI SQL type such as CHARACTER or REAL such as CHARACTER or REAL

With a map method, you can order With a map method, you can order any number of objects by calling each any number of objects by calling each object's map method once object's map method once


Map MethodsMap Methods

a map method is simply a parameter-a map method is simply a parameter-less member functionless member function

uses the MAP keyworduses the MAP keyword returns one of the datatypes just listed returns one of the datatypes just listed What makes a map method special is What makes a map method special is

that, if an object type defines one, the that, if an object type defines one, the method is called automatically to method is called automatically to evaluate such comparisons as obj_1 > evaluate such comparisons as obj_1 > obj_2 obj_2


Map MethodMap Method

Where obj_1 and obj_2 are two Where obj_1 and obj_2 are two object variables that can be object variables that can be compared using a map method compared using a map method map(), the comparison:map(), the comparison:

obj_1 > obj_2obj_1 > obj_2

is equivalent to:is equivalent to:

obj_1.map() > obj_2.map()obj_1.map() > obj_2.map()


Map MethodMap Method


Order MethodOrder Method

Order methods make direct object-Order methods make direct object-to-object comparisons to-object comparisons

Unlike map methods, they cannot Unlike map methods, they cannot map any number of objects map any number of objects

They simply tell you that the current They simply tell you that the current object is less than, equal to, or object is less than, equal to, or greater than the other object that it greater than the other object that it is being compared to, with respect is being compared to, with respect to the criterion used by the method to the criterion used by the method


Order MethodOrder Method


Question at the StageQuestion at the Stage

What are the methods used to What are the methods used to compare Oracle objects? Can you compare Oracle objects? Can you give two examples to define them?give two examples to define them?

What are the differences between What are the differences between map method and order method?map method and order method?


ReferenceReference

Oracle 10g User manual for Object Oracle 10g User manual for Object Oriented Data ModelOriented Data Model

www.wikipedia.orgwww.wikipedia.org


AcknowledgementAcknowledgement

Nick Whittaker, Lecturer, University Nick Whittaker, Lecturer, University of Manchester, UKof Manchester, UK

l14 l15 oo dbms

Technology

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data type

kuet object methods

object procedures

methodsan object