PL/SQL and the Table API

Benefits of Server-Side CodeSpeedy Pizza

MENUNAPOLITAINE

PIZZA

• Reduced network traffic

• Maintainability• Data integrity

TriggersProceduresFunctionsPackages

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

What Is a Database Trigger?

ITEMS

DMLDMLactionaction

Database TriggerCode that is implicitly executed when an INSERT, UPDATE, or DELETE statement is issued against its associated table or view

• When

– Before DML

– After DML

• What

– Row

– Statement

TriggerTrigger

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

RENTALS

PublicDefinitions

Packages

1+ 1

2

Procedures

Functions

Public andPrivate Elements

BodyBodyActionAction

Value = 2Value = 2

SpecificationSpecification

PL/SQL in the Repository

APPLICATION[1]

Relational Table Definitions

PL/SQL Definitions

PL/SQL Composition

Navigator - Server ModelNavigator - Server Model

Server Model Distribution

Triggers

Functions

Procedures

Triggers

Packages Structure

Implementation

PL/SQL Definitions

PL/SQL DefinitionsFunction DefinitionsPackage DefinitionsProcedure Definitions

Cursor DefinitionsTrigger DefinitionsUndefined PL/SQL

Server Model

ArgumentsSub Program UnitsProgram DataDatastructuresSynonyms

P_SET_PRICE

CREATE . . . ( p_name IN VARCHAR2) IS

v_date DATE; TYPE table_type IS . . .BEGIN IF . . . THEN . . . ; . . . callprocedure(v_date); . . .END;

Navigator - Server ModelNavigator - Server Model

PL/SQL Definitions

PL/SQL Composition

Server Model

Relational Table DefinitionsAPPLICATION[1]

TITLES

TriggersTRIG1

Columns

Trigger LogicTRIG1

TRIG1

PL/SQL DefinitionsTrigger Definitions

Trigger Header Definition

PL/SQL DefinitionCompleteEnabledTrigger . . .When Condition

. . .PL/SQL Block. . .

PL/SQL Logic

Defining Triggers

PL/SQL Definitions

Procedure DefinitionsP_SET_PRICE

Navigator - Server Model

Opening the Logic Editor• Drag the definition to the work

surface

Using the Logic Editor

PROCEDURE

PL/SQL PROCEDURE

Select

INTO

FROM

WHERE

SELECT title

INTO v_title

FROM titles

WHERE product_code = p_product_code;...

SELECT

OutlinerOutliner

Text EditorText Editor

PL/SQL

Root

Constructs

Statements

Static Data

Construct TreeConstruct Tree

Generating PL/SQL ObjectsDDL file:• CREATE OR

REPLACE statements

• Header• Data declarations• PL/SQL logic

Use the utility as you would for Use the utility as you would for other database objectsother 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

Validation code

Application

Tables Tables

Table API

Tables

Table API Triggers

Triggers

• Fire on insert, update, or delete

• Call the server packages

Table API Packages

• Are called by:– Applications– Triggers

• Perform DML operations• Validate data• Derive column values

ServerPackages

Server PackagesPackage cg$titles

Insert

Update

Delete

Lock

procedures . . .callcg$titles.ins Insert

TITLES

# * PROD_CDE * TITLE . . .

TITLES

# * PROD_CDE * TITLE . . .

In-sert

trigger

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

TABLEColumn_1Column_2

Server

Packages

Form BuilderForm Builderapplicationapplication

Triggers

WebServerWebServerapplicationapplication

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.