university of sunderland com 220 lecture six slide 1 building interactive forms applications using...

University of Sunderland COM 220 Lecture Six Slide 1

Building Interactive Forms Building Interactive Forms ApplicationsApplicationsusing Oracleusing Oracle


Developer 6iDeveloper 6i

• All databases have some kind of interface• Oracle implementation is Developer 6i

– Allows non-programmers to access the DB by entering values on a form

– 4GL Tool - much of the work is done for you– Usually a form would be developed for each

transaction within a system– 2 modes -a Designer Mode and an Operator

mode



Forms Designer

• Define transactions that combine data from multiple tables into a single form

• Quickly create default forms using a full set of defaults

• Customize all aspects of an application design

• Supports master/detail relationships



• A Forms application consist of objects• Objects contain information needed to

manipulate and produce an application• Oracle forms contains many different types

of object, e.g. Blocks, items, triggers, buttons, graphics



• A number of tools exist in order to manipulate these objects:

– Object Navigator

– Layout Editor

– Properties Window

– PL/SQL Editor



• Object Navigator– Provides a hierarchical view of all objects in a

form– used to create new objects– used to select existing objects

• Layout Editor– Provides a means of graphically displaying the

form– used to change a forms appearance - move

fields around etc



• Properties Editor– All objects on a form have properties– Used to change the characteristics of objects,

such as height and width, font, colour, capitals etc

• PL/SQL Editor– Used to write programs (called triggers) to add to

the functionality of a form


PL/SQL & TriggersPL/SQL & Triggers

WHAT IS A TRIGGER ?

• Piece of custom code that is executed by an FORMS event

• Contains PL/SQL code.

• Every trigger has a name

• Name corresponds to an event


TriggersTriggers

WHERE CAN A TRIGGER BE USED ?

Within a form at :

– FORM LEVEL– BLOCK LEVEL– ITEM LEVEL


Object NavigatorObject Navigator


Triggers UsesTriggers Uses

WHAT CAN A TRIGGER BE USED FOR?

• Perform data validation, data entry and data deletion.

• Control the logical flow of the application.


Events ExamplesEvents Examples

• Pressing a button (WHEN-BUTTON-PRESSED)• Pressing tab key (KEY-NEXT-ITEM) • Leaving the item (POST-TEXT-ITEM)• Enter the block (PRE-BLOCK)• Ready record for Input (WHEN-NEW-RECORD-

INSTANCE)


Example EventExample Event

• EXAMPLE :

KEY-NEXT-ITEM is a trigger used at item level. It is fired when the next item key (return or tab) is pressed. The normal function of the next item key is replaced by the code contained within the trigger


PL/SQLPL/SQL

WHAT IS PL / SQL ?

– A programming language composed of procedural and non-procedural constructs.

– It is based around the ADA programming language

– Designed to augment SQL*PLUS


PL/SQL BlockPL/SQL Block

• THE PL/SQL BLOCK

– A PL/SQL program is known as a block - short for “block of code”.

– The PL/SQL block is composed of 4 sections:• DECLARE

• BEGIN

• EXCEPTION

• END


PL/SQL BlocksPL/SQL Blocks

PL/SQL BLOCK SECTIONS:

DECLARE

Declarative statements

BEGIN

Executable statements

EXCEPTION

Exception handlers

END;



DECLARE SECTION• Variables, constants and cursors to be used

in the block are used here.• Variables and constants must be defined

before they can be used.DECLAREsurname char(10);n1 number := 23.4567;joindate date;enddate date := ‘28-jan-95’;



• BEGIN SECTION– This tells oracle that executable statements follow.– Can be nested up to 200 levels.– Must be terminated by an end section

beginselect surnameinto :b1.surnamefrom tenantwhere :b1.property_id =

property_id;end;



EXCEPTION SECTION• Contains routines for handling exception

conditions.• There are two kinds of exception:-

Pre-defined

User-defined

THIS SECTION IS OPTIONAL


PL/SQL ExamplePL/SQL Example

DECLARE

too_old exception;

BEGIN

if :b1.age > 35 then

raise too_old;

EXCEPTION

when too_old then

message (‘You are past it!’);

END;



END SECTION

All PL/SQL blocks must have an end

statement followed by a ;


Further ReadingFurther Reading

• Developing Oracle Forms– COM220 Unit 2 - Introduction to Forms Part I– PL/SQL and Triggers– COM220 Unit 4 - Introduction to Forms Part II

• Next Week– Database Users and Administration

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