University of Sunderland COM 220 Lecture Six Slide 1 Building Interactive Forms Applications using Oracle

University of Sunderland COM 220 Lecture Six Slide 2 Developer 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

University of Sunderland COM 220 Lecture Six Slide 3 Developer 6i 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

University of Sunderland COM 220 Lecture Six Slide 4 Developer 6i 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

University of Sunderland COM 220 Lecture Six Slide 5 Developer 6i A number of tools exist in order to manipulate these objects: –Object Navigator –Layout Editor –Properties Window –PL/SQL Editor

University of Sunderland COM 220 Lecture Six Slide 6 Developer 6i 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

University of Sunderland COM 220 Lecture Six Slide 7 Developer 6i 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

University of Sunderland COM 220 Lecture Six Slide 8 PL/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

University of Sunderland COM 220 Lecture Six Slide 9 Triggers WHERE CAN A TRIGGER BE USED ? Within a form at : –FORM LEVEL –BLOCK LEVEL –ITEM LEVEL

University of Sunderland COM 220 Lecture Six Slide 10 Object Navigator

University of Sunderland COM 220 Lecture Six Slide 11 Triggers Uses WHAT CAN A TRIGGER BE USED FOR? Perform data validation, data entry and data deletion. Control the logical flow of the application.

University of Sunderland COM 220 Lecture Six Slide 12 Events 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)

University of Sunderland COM 220 Lecture Six Slide 13 Example 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

University of Sunderland COM 220 Lecture Six Slide 14 PL/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

University of Sunderland COM 220 Lecture Six Slide 15 PL/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

University of Sunderland COM 220 Lecture Six Slide 16 PL/SQL Blocks PL/SQL BLOCK SECTIONS: DECLARE Declarative statements BEGIN Executable statements EXCEPTION Exception handlers END;

University of Sunderland COM 220 Lecture Six Slide 17 PL/SQL Blocks 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. DECLARE surnamechar(10); n1 number := ; joindatedate; enddatedate := ‘28-jan-95’;

University of Sunderland COM 220 Lecture Six Slide 18 PL/SQL Blocks BEGIN SECTION –This tells oracle that executable statements follow. – Can be nested up to 200 levels. – Must be terminated by an end section begin select surname into :b1.surname from tenant where :b1.property_id = property_id; end;

University of Sunderland COM 220 Lecture Six Slide 19 PL/SQL Blocks EXCEPTION SECTION Contains routines for handling exception conditions. There are two kinds of exception:- Pre-defined User-defined THIS SECTION IS OPTIONAL

University of Sunderland COM 220 Lecture Six Slide 20 PL/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;

University of Sunderland COM 220 Lecture Six Slide 21 PL/SQL Blocks END SECTION All PL/SQL blocks must have an end statement followed by a ;

University of Sunderland COM 220 Lecture Six Slide 22 Further 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