Lesson 9

This module discussed the object-relational approach using Oracle. You have learned about object details that help you build the program logic.
Now that you have completed this module, you should be able to:

1. Understand the reasons to use Oracle objects versus relational tables
2. Understand the different terms for Oracle objects
3. Describe the SQL techniques that allow you to query object tables
4. Determine when to use collections and variable size arrays
5. Determine when to use nested tables in querying
6. Write SQL to query object tables

In this module, you were introduced to the following glossary terms:

1. Aggregation: Aggregation occurs where one object is composed, at least in part, of other objects; you may call it a part-of relationship. A tail is a part-of a dog or a piston is a part-of an engine. This concept is implemented within collections.
2. Application Programming Interface: An API is designed to allow quick and easy integration of different programming languages like C, Java, and so on, with the Oracle 8i database and its development environment.
3. Composition: A composition embodies the concept of a column within a table is a combination of several composite columns.
   This concept cannot be handled within a relational database. In Oracle8i, it is possible with object types and collections such as varrays and nested table.
4. Dot notation: To reference individual fields within the record, use the dot notation. A dot (.) serves as the selector for the individual field name.
5. Encapsulation: Encapsulation is the concept of information hiding. Encapsulation asserts that you can only "get at" the contents of the object using predefined functions. This allows the programmer to retain control of the data and helps reduce the impact on changes to the schema.
6. Enumeration: An enumeration is a data type which can be given a finite (usually small) set of named values. Therefore, enumerations are useful for representing real world values that naturally have a finite set of values, each of which has a meaningful name.
7. Homogenous: Homogenous means elements of the same data type.
8. Inheritance: Inheritance is a technique used within object-oriented development to create objects that contain generalized attributes and behavior for groups of related objects. The more general objects created using inheritance are referred to as super-types. The objects that inherit from the super-types (that is, they are more specific cases of the super-type) are called subtypes.
9. Object-relational: The object-relational model allows users to define object types, specifying both the structure of the data and the methods of operating on the data, and to use these datatypes within the relational model.
10. Persistent object: An object that is stored or saved. Within Oracle, an object is stored within the database.
11. REPLACE: CREATE OR REPLACE is the syntax for creating procedures, functions, or object types. It means that if the object type / procedure already exists within the database, the DDL statement should replace the existing object type / procedure.
12. Sparse: Sparse means lesser number of elements or records.
13. Transient object: A transient object is an instance of an object type. It may have an object identifier, and it has a lifetime which is determined by the application when the instance is created. The application can also delete a transient object at any time. Transient objects are often created by the application to store temporary values for computation. Transient objects cannot be converted to persistent objects. Their role is fixed at the time they are instantiated.

Click the Quiz link below to take a multiple-choice quiz about the material we have covered in this module.
Querying Object Tables - Quiz
In the next module, we will go into more detail on querying related object tables.