Triggers for audit control

Question

Good morning all,
I am in desperate need of a trigger for audit control, that is who is doing what action (udpate, delete, insert)to a record, old value, and new value. Time and date wouild also be helpful.
Problem -- and it's a big one. I don't know pl/sql. Trying to learn it, but in time for this project.
Thanks all.
P.S. If you have a link to a documentation that tells you how to do something like this, please let me know. Thanks again.

Answer 1

Hi,
The following example demonstrates a trigger that audits modifications to the Emp_tab table for each row. It requires that a "reason code" be stored in a global
package variable before the update. This shows how triggers can be used to provide value-based auditing and how to use public package variables.
Note:
You may need to set up the following data structures for the examples to work:
CREATE OR REPLACE PACKAGE Auditpackage AS
Reason VARCHAR2(10);
PROCEDURE Set_reason(Reason VARCHAR2);
END;
CREATE TABLE Emp99 (
Empno NOT NULL NUMBER(4)
Ename VARCHAR2(10)
Job VARCHAR2(9)
Mgr NUMBER(4)
Hiredate DATE
Sal NUMBER(7,2)
Comm NUMBER(7,2)
Deptno NUMBER(2)
Bonus NUMBER
Ssn NUMBER
Job_classification NUMBER);
CREATE TABLE Audit_employee (
Oldssn NUMBER
Oldname VARCHAR2(10)
Oldjob VARCHAR2(2)
Oldsal NUMBER
Newssn NUMBER
Newname VARCHAR2(10)
Newjob VARCHAR2(2)
Newsal NUMBER
Reason VARCHAR2(10)
User1 VARCHAR2(10)
Systemdate DATE);
CREATE OR REPLACE TRIGGER Audit_employee
AFTER INSERT OR DELETE OR UPDATE ON Emp99
FOR EACH ROW
BEGIN
/* AUDITPACKAGE is a package with a public package
variable REASON. REASON could be set by the
application by a command such as EXECUTE
AUDITPACKAGE.SET_REASON(reason_string). Note that a
package variable has state for the duration of a
session and that each session has a separate copy of
all package variables. */
IF Auditpackage.Reason IS NULL THEN
Raise_application_error(-20201, 'Must specify reason'
|| ' with AUDITPACKAGE.SET_REASON(Reason_string)');
END IF;
/* If the above conditional evaluates to TRUE, the
user-specified error number and message is raised,
the trigger stops execution, and the effects of the
triggering statement are rolled back. Otherwise, a
new row is inserted into the predefined auditing
table named AUDIT_EMPLOYEE containing the existing
and new values of the Emp_tab table and the reason code
defined by the REASON variable of AUDITPACKAGE. Note
that the "old" values are NULL if triggering
statement is an INSERT and the "new" values are NULL
if the triggering statement is a DELETE. */
INSERT INTO Audit_employee VALUES
(:old.Ssn, :old.Ename, :old.Job_classification, :old.Sal,
:new.Ssn, :new.Ename, :new.Job_classification, :new.Sal,
auditpackage.Reason, User, Sysdate );
END;
Optionally, you can also set the reason code back to NULL if you wanted to force the reason code to be set for every update. The following simple AFTER statement
trigger sets the reason code back to NULL after the triggering statement is run:
CREATE OR REPLACE TRIGGER Audit_employee_reset
AFTER INSERT OR DELETE OR UPDATE ON Emp_tab
BEGIN
auditpackage.set_reason(NULL);
END;
Hope that helps.
Thanks,
Sharmila