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PL/SQL and the Table API
Benefits of Server-Side Code
Speedy Pizza
MENU
PIZZA
NAPOLITAINE
Triggers
Procedures
Functions
Packages
• Reduced
network traffic
• Maintainability
• Data integrity
Older Editions of Designer
• Most constraints only enforced in
application
• Server vulnerable to other access
methods
• Application code references tables
and generates network traffic
Database Trigger
• NOT a form trigger
– When-enter-block, When-validate-item…
•
•
•
•
•
Occurs in server
Associated with Lock or DB modification
Before or After DB event
For every affected Row, or
For SQL Statement
DML
action
What Is a Database
Trigger?
Trigger
•
When
– Before DML
ITEMS
– After DML
•
What
– Row
– Statement
Database Trigger
Code that is implicitly executed when an INSERT,
UPDATE, or DELETE statement is issued against
its associated table or view
Triggers and Packages
• Triggers often call procedures in Packages
• Packages provide Scope for Variables
shared by Procedures
• Each process gets own copy of Package
Variables
Packages
RENTALS
Public
Definitions
Body
Procedures
1
+1
2
Specification
Action
Functions
Public and
Private
Elements
Value = 2
PL/SQL in the Repository
Navigator - Server Model
Server Model
Distribution
Implementation
APPLICATION[1]
Relational Table Definitions
PL/SQL Definitions
PL/SQL Composition
Triggers
Functions
Procedures
Triggers
Structure
Packages
PL/SQL Definitions
Server Model
PL/SQL Definitions
Function Definitions
Package Definitions
Procedure Definitions
P_SET_PRICE
Arguments
Sub Program Units
Program Data
Datastructures
Synonyms
Cursor Definitions
Trigger Definitions
Undefined PL/SQL
CREATE . . . (
p_name IN VARCHAR2) IS
v_date DATE;
TYPE table_type IS . . .
BEGIN
IF . . . THEN . . . ;
...
callprocedure(v_date);
...
END;
Defining Triggers
Navigator - Server Model
Server Model
APPLICATION[1]
Relational Table Definitions
TITLES
Triggers
TRIG1
Columns
Trigger Header
Definition
PL/SQL Definition
Complete
Enabled
Trigger . . .
When Condition
Trigger Logic
TRIG1
PL/SQL Definitions
Definitions
PL/SQL
TriggerComposition
Definitions
PL/SQL
TRIG1
...
PL/SQL Block
...
PL/SQL
Logic
Opening the Logic Editor
• Drag the definition to the work surface
Navigator - Server Model
PL/SQL Definitions
Procedure Definitions
P_SET_PRICE
Using the Logic Editor
PL/SQL PROCEDURE
PROCEDURE
Select
SELECT
INTO
FROM
WHERE
Outliner
SELECT title
Text Editor
INTO v_title
FROM titles
WHERE product_code =
PL/SQL p_product_code;
...
Construct Tree
Root
Constructs
Statements
Static Data
Generating PL/SQL Objects
DDL file:
• CREATE OR
REPLACE
statements
• Header
• Data declarations
• PL/SQL logic
Use the utility as you would for
other database objects
Fortunately ...
• You do not have to write most
triggers or packages
• Designer writes them for you
• You give specifications
• You generate Table API
• All this code used to be in
Applications
Table API Keeps Applications
Thin Application
Application
Table API
Tables
Tables
Validation code
Table API Triggers
• Fire on insert, update, or
delete
• Call the server packages
Triggers
Table API Packages
• Are called by:
– Applications
– Triggers
• Perform DML operations
• Validate data
• Derive column values
Server Packages
Package cg$titles
procedures . . .
call
cg$titles.ins
Insert
TITLES
# * PROD_CDE
* TITLE
...
Update
Delete
Lock
trigger
Insert
Why API?
• Table API provides a Table Handler
for each package
• Normal DML causes Triggers to
Invoke Handlers
• Applications can call API procedures
directly
– Disabling recursive call of trigger
Applications and the API
Triggers
Form Builder
application
WebServer
application
TABLE
Column_1
Column_2
Customization
• API handles many standard
Requirements.
• You can add code to API for special
Requirements.
• Even specify whether it is called
before or after standard handling.