ITEC 4220 - L3: Object-Relational DBMSs (Oracle 19c)

ORDBMS (Object-Relational DBMS)

A relational DBMS extended with object features like user-defined types methods complex objects and limited inheritance behavior.

Oracle object type (ADT)

A user-defined type created with AS OBJECT that bundles attributes and method signatures into one datatype.

Object type specification

The CREATE TYPE definition that lists attributes and declares methods without the method code.

Object type body

The CREATE TYPE BODY definition that contains the implementation code for the methods declared in the type specification.

Attribute in an object type

A named property stored inside an object instance such as id name or date.

Method in an object type

An operation associated with an object type that can read or modify the object’s state.

MEMBER method

An instance method that runs on a specific object instance and can access its attributes using SELF.

STATIC method

A type-level method that is not tied to a particular instance and does not use SELF as an instance reference.

FUNCTION method

A method that returns a value and can be used in expressions and SELECT statements.

PROCEDURE method

A method that performs an action and returns no value.

SELF

Implicit reference to the current object instance inside a member method implementation.

Object constructor call

Creating an object by calling the type name like a function and passing attribute values in order.

Public object attributes in Oracle

Attributes are directly readable with SELECT and directly changeable with UPDATE rather than being hidden behind getters.

Built-in character types (Oracle)

Common string datatypes such as CHAR NCHAR VARCHAR2 and NVARCHAR2.

Built-in numeric and date types (Oracle)

Common scalar datatypes such as NUMBER DATE and TIMESTAMP used for object attributes.

Large object types (Oracle)

Datatypes for large text or binary data such as CLOB and BLOB.

RAW and LONG RAW (Oracle)

Binary datatypes for storing raw bytes often used for legacy or specific binary fields.

MAP method

A special method that returns a scalar value used to compare and sort object instances.

ORDER method

A special method that directly compares two objects and returns a negative zero or positive integer.

MAP method signature pattern

MAP MEMBER FUNCTION returning a scalar datatype and taking no parameters.

ORDER method signature pattern

ORDER MEMBER FUNCTION taking an object parameter and returning INTEGER for comparison ordering.

MAP vs ORDER exclusivity rule

Only one of MAP or ORDER can be defined for a given object type.

MAP or ORDER in a hierarchy rule

Comparison logic using MAP or ORDER must be declared in the supertype when a type has subtypes.

Nested object type

An object type used as an attribute inside another object type creating embedded structured values.

Row object

An object instance stored as a row in an object table and treated as a database object with an identifier.

OID (Object Identifier)

System-managed identity for row objects in an object table that is independent of attribute values.

Nested object OID rule

Embedded nested objects are treated like literal values and do not have their own OIDs.

REF type

A reference datatype that stores a pointer-like reference to a row object of a specified object type.

REF column

An attribute or table column declared as REF TypeName used to reference an object stored in an object table.

DEREF

Oracle operation that follows a REF and returns the referenced object instance.

VALUE(alias)

Oracle operation that returns the full object value for rows from an object table alias.

TREAT

Oracle operation used to treat an object or REF as a specific subtype so subtype-only attributes or methods can be accessed.

Incomplete object type

A forward declaration created with CREATE TYPE TypeName to break circular dependency during type creation.

Circular reference problem

A design where two types reference each other requiring forward declaration before full definitions.

Object table

Creating a table whose rows are objects using CREATE TABLE table_name OF object_type.

Extent in Oracle object tables

The set of all row objects stored in an object table for a given object type.

System-generated OID option

Using OBJECT IDENTIFIER IS SYSTEM GENERATED so Oracle assigns row object identity automatically.

SCOPE IS constraint

A constraint on a REF column that restricts referenced objects to come from a specific object table.

Primary key constraint on object tables

A uniqueness constraint that can be applied to object attributes when needed for business keys.

REF primary key restriction

A REF attribute cannot be used as the primary key for an object table.

CHECK constraint

Constraint that enforces a boolean condition on attribute values in object tables.

NOT NULL constraint

Constraint that prevents NULL values in selected attributes or columns.

UNIQUE constraint

Constraint that enforces uniqueness of attribute values across rows.

ALTER TABLE on object tables

Using ALTER TABLE to add modify or drop constraints on an object table.

DROP TABLE CASCADE approach

Dropping a table while removing dependent constraints or references that would otherwise block the drop.

Insert object with constructor

INSERT pattern that uses TypeName(value1 value2 ...) to populate an object table row.

Nested constructor insertion

Creating complex objects by calling constructors inside other constructors for nested object attributes.

REF retrieval for insert

Creating a REF value by selecting REF(alias) from the referenced object table.

Two-step REF assignment

Inserting with NULL for a REF column then updating it using a subquery that returns REF(alias).

Dot notation for attributes

Accessing an attribute of an object value using alias.object_column.attribute_name.

Updating object attributes

UPDATE statements can change object attributes directly using dot notation on the object column.

Update scope limitation

An UPDATE statement can modify only one target table at a time even when objects reference other tables.

Referenced object update rule

Updating the attributes of a referenced object is done through its own object table not through the REF holder.

Deleting objects from an object table

Removing row objects with DELETE while handling dependent references according to constraints and design.

Object-relational complex object support

Support for structured nested values and collections without forcing everything into flat tables.

Object-relational identity support

Support for object identity via OID and referencing via REF to model relationships more directly.

Single inheritance in Oracle object types

Oracle object types support one direct supertype for a subtype rather than multiple inheritance.

FINAL type

A type that cannot have subtypes and is the default if NOT FINAL is not specified.

NOT FINAL type

A type that allows subtypes to be defined under it enabling inheritance.

ALTER TYPE NOT FINAL

Changing a type definition so it can have subtypes when the design evolves.

NOT INSTANTIABLE type

An abstract type that cannot be directly constructed into instances and has no constructor.

Instantiable type

A concrete type that can be used to create object instances and store them in object tables.

Object table creation rule for instantiability

Object tables are created only for instantiable types not for abstract types.

Overloading

Same method name with different parameter lists allowing multiple versions of an operation.

Overriding

Providing a new implementation for an inherited member method in a subtype.

Hiding

Redefining a static method name in a subtype which hides the supertype static method.

OVERRIDING keyword requirement

Subtypes must explicitly declare OVERRIDING when overriding a member method in Oracle.

Final method restriction

Only member methods declared NOT FINAL are eligible to be overridden in subtypes.

Non-instantiable method

A method declared in an abstract type that subtypes must implement or override before instances can use it.

Subtype extension

Adding new attributes or methods in a subtype while inheriting all supertype features.

Inherited features propagation

Changes to a supertype are inherited by subtypes so the hierarchy stays consistent.

Polymorphic access via TREAT

Accessing subtype-specific attributes or methods by treating a supertype reference as a subtype.

REF-based relationship modeling

Representing relationships by storing REFs rather than foreign keys to enable object-style navigation.

SCOPE-based referential control

Limiting where a REF can point to by enforcing a specific target object table.

MAP-based ordering behavior

Object ordering defined by mapping objects to a scalar value used in ORDER BY and comparisons.

ORDER-based ordering behavior

Object ordering defined by comparing two objects and returning an integer ranking.