Triggers : Trigger « Trigger « Oracle PL/SQL Tutorial

Oracle PL/SQL Tutorial
1. Introduction
2. Query Select
3. Set
4. Insert Update Delete
5. Sequences
6. Table
7. Table Joins
8. View
9. Index
10. SQL Data Types
11. Character String Functions
12. Aggregate Functions
13. Date Timestamp Functions
14. Numerical Math Functions
15. Conversion Functions
16. Analytical Functions
17. Miscellaneous Functions
18. Regular Expressions Functions
19. Statistical Functions
20. Linear Regression Functions
21. PL SQL Data Types
22. PL SQL Statements
23. PL SQL Operators
24. PL SQL Programming
25. Cursor
26. Collections
27. Function Procedure Packages
28. Trigger
29. SQL PLUS Session Environment
30. System Tables Data Dictionary
31. System Packages
32. Object Oriented
33. XML
34. Large Objects
35. Transaction
36. User Privilege
Java
Java Tutorial
Java Source Code / Java Documentation
Java Open Source
Jar File Download
Java Articles
Java Products
Java by API
Photoshop Tutorials
Maya Tutorials
Flash Tutorials
3ds-Max Tutorials
Illustrator Tutorials
GIMP Tutorials
C# / C Sharp
C# / CSharp Tutorial
C# / CSharp Open Source
ASP.Net
ASP.NET Tutorial
JavaScript DHTML
JavaScript Tutorial
JavaScript Reference
HTML / CSS
HTML CSS Reference
C / ANSI-C
C Tutorial
C++
C++ Tutorial
Ruby
PHP
Python
Python Tutorial
Python Open Source
SQL Server / T-SQL
SQL Server / T-SQL Tutorial
Oracle PL / SQL
PostgreSQL
SQL / MySQL
MySQL Tutorial
VB.Net
VB.Net Tutorial
Flash / Flex / ActionScript
VBA / Excel / Access / Word
XML
XML Tutorial
Microsoft Office PowerPoint 2007 Tutorial
Microsoft Office Excel 2007 Tutorial
Microsoft Office Word 2007 Tutorial
Oracle PL/SQL Tutorial » Trigger » Trigger 
28. 2. 1. Triggers

A trigger is a procedure that is run automatically by the database when a specified SQL DML INSERT, UPDATE, or DELETE statement is run against a table.

Triggers are useful for doing things like advanced auditing of changes made to column values in a table.

When a Trigger Runs

  1. A trigger can fire before or after the SQL statement runs.
  2. A trigger can may be run once for every row affected. Such a trigger is known as a row-level trigger.
  3. A trigger can may be run for all the rows. Such trigger is known as a statement-level trigger.
  4. A row-level trigger has access to the old and new column values when the trigger fires as a result of an UPDATE statement on that column.
  5. The firing of a trigger may also be limited using a trigger condition.

Different events may fire a trigger, but these events are always divided into three groups:

  1. DML triggers,
  2. INSTEAD OF triggers, and
  3. system event triggers.

DML triggers are the triggers on INSERT/UPDATE/DELETE operations in any table.

SQL> CREATE TABLE employee_history (
  2     name VARCHAR2(100),
  3     description VARCHAR2(255),
  4     occurred_on DATE);

Table created.

SQL>
SQL>
SQL> CREATE TABLE employee_compensation (
  2     company VARCHAR2(100),
  3     name VARCHAR2(100),
  4     compensation NUMBER,
  5     layoffs NUMBER);

Table created.

SQL>
SQL>
SQL> CREATE OR REPLACE PROCEDURE employee_audit (
  2     name IN VARCHAR2,
  3     description IN VARCHAR2,
  4     occurred_on IN DATE
  5     )
  6  IS
  7     PRAGMA AUTONOMOUS_TRANSACTION;
  8  BEGIN
  9     INSERT INTO employee_history VALUES (
 10        employee_audit.name,
 11        employee_audit.description,
 12        employee_audit.occurred_on
 13        );
 14     COMMIT;
 15  END;
 16  /

Procedure created.

SQL>
SQL>
SQL>
SQL> CREATE OR REPLACE TRIGGER bef_ins_ceo_comp
  2  BEFORE INSERT ON employee_compensation FOR EACH ROW
  3  DECLARE
  4     ok BOOLEAN := TRUE;
  5  BEGIN
  6     IF ok
  7     THEN
  8        employee_audit (
  9           :new.name, 'BEFORE INSERT', SYSDATE);
 10     END IF;
 11  END;
 12  /

Trigger created.

SQL>
SQL>
SQL>
SQL> SELECT name,
  2         description,
  3         TO_CHAR (occurred_on, 'MM/DD/YYYY HH:MI:SS') occurred_on
  4    FROM employee_history;

no rows selected

SQL>
SQL> BEGIN
  2     INSERT INTO employee_compensation VALUES ('M''J'91000002700);
  3
  4     INSERT INTO employee_compensation VALUES ('A''H'332000003300);
  5
  6     INSERT INTO employee_compensation VALUES ('E''G'1070000020100);
  7
  8  END;
  9  /

PL/SQL procedure successfully completed.

SQL>
SQL> SELECT name,
  2         description,
  3         TO_CHAR (occurred_on, 'MM/DD/YYYY HH:MI:SS') occurred_on
  4    FROM employee_history;

NAME
--------------------------------------------------------------------------------
DESCRIPTION
--------------------------------------------------------------------------------
OCCURRED_ON
-------------------
J
BEFORE INSERT
07/24/2008 08:03:08

H
BEFORE INSERT
07/24/2008 08:03:08

NAME
--------------------------------------------------------------------------------
DESCRIPTION
--------------------------------------------------------------------------------
OCCURRED_ON
-------------------

G
BEFORE INSERT
07/24/2008 08:03:08


SQL>
SQL>
SQL> DROP TABLE employee_compensation;

Table dropped.

SQL>
SQL> DROP TABLE employee_history;

Table dropped.
28. 2. Trigger
28. 2. 1. Triggers
28. 2. 2. System triggers
28. 2. 3. Creating a Trigger
28. 2. 4. Trigger Blocks
28. 2. 5. Trigger that output old value
28. 2. 6. DML Trigger Example
28. 2. 7. Firing a Trigger
28. 2. 8. The use of a trigger
28. 2. 9. INSERTING, DELETING and UPDATING Predicates
28. 2. 10. Reference current user name in trigger
28. 2. 11. Call raise_application_error to report an error in a trigger
28. 2. 12. Use cursor in trigger
28. 2. 13. Check the status of the trigger
28. 2. 14. Show errors for a trigger
www.java2java.com | Contact Us
Copyright 2009 - 12 Demo Source and Support. All rights reserved.
All other trademarks are property of their respective owners.