In Part 1 of this series, we talked about how Oracle objects compare to Java and how to create Oracle Objects. In Part 2, I covered we covered object comparison and type inheritance. Today, we’ll talk about polymorphism and type evolution.

Like parts 1 and 2, this will be a technical discussion.

Polymorphism

First a definition. What is Polymorphism and why is it important? One of the best definitions I have found is this link at OnJava. You can skip the part about object serialization. Not really that important to Oracle’s OO as you’re already in the database.

Let’s go back to our (most basic) calculator example.

CREATE OR REPLACE TYPE Calculator AS OBJECT (
  value NUMBER,
  MEMBER PROCEDURE print,
  MEMBER PROCEDURE add1( p_amt IN NUMBER ),
  MEMBER PROCEDURE subtract( p_amt IN NUMBER )
  )
  NOT FINAL;
/

CREATE OR REPLACE TYPE BODY Calculator AS
  MEMBER PROCEDURE print IS
  BEGIN
    DBMS_OUTPUT.PUT_LINE( TO_CHAR( value ) );
  END;

  MEMBER PROCEDURE add1( p_amt IN NUMBER )  IS
  BEGIN
    value := value + p_amt;
  END;

  MEMBER PROCEDURE subtract( p_amt IN NUMBER )  IS
  BEGIN
    value := value - p_amt;
  END;

END;
/

And our Advanced Calculator:

CREATE OR REPLACE TYPE AdvancedCalculator UNDER Calculator (
  pi FLOAT,
  CONSTRUCTOR FUNCTION AdvancedCalculator
     RETURN SELF AS RESULT ,
  MEMBER PROCEDURE multiply( p_amt IN NUMBER ),
  MEMBER PROCEDURE divide( p_amt IN NUMBER ),
  OVERRIDING MEMBER PROCEDURE print
   )
NOT FINAL;
/

This isn’t exactly the same AdvancedCalculator.

This is a continuation of Object Orientation in Oracle. I guess I should have called it the Sorcerer of OOO. This is a technical entry.

Anyway, in part 1 I covered the basics of creating an Oracle object type and showing how it compared to a Java class. Today I’m going to cover the concepts of comparing objects and Inheritance. In part 3, I will cover type evolution and Polymorphism and in part 4 I will cover Object Views and Object Tables.

Comparing Objects

Many times, you will be working with multiple instances of the same object.

This is part 4 of a 3 part series. Heh I guess this qualifies as a little lagniappe on security and audit. I could have called this Oracle Audit but I already spoke about audit in Part 3. I just decided to continue on in the series.

This is a brief, technical discussion about the implementation of audit in Oracle 10g. I’ll quickly show how to turn on standard audit and how to see some of the audit taking place. I’ll follow that with an implementation of FGA and finally a trigger based audit.

One aspect of auditing is to audit your administrators.

Regardless of any regulations you are required to meet you can implement a security and audit scheme that will cover you for most, if not all, eventualities. Having good security and auditability should be desirable regardless of regulations. It protects your business.

In parts 1 and 2, I covered the security side of it. So what do I mean by Audit? Well, auditing is knowing what’s going on in your environment. Future research requirements, accountability, error correction, etc are all covered by audit.

So how does Oracle implement audit? There are several ways you can do it: Standard Audit, Fine Grained Audit and Trigger Based Audit.