Tutorials: Creating Forms: Creating Oracle Forms

NYU course on Forms Intro to Oracle Forms Developer (NYU)

OOP & Terms

CLASS:
a class describes the contents of the objects that belong to it: it describes an aggregate of data fields (called instance variables), and defines the operations (called methods).

A class is a blueprint or prototype that defines the variables and the methods common to all objects of a certain kind.

CLASS HIERARCHY: is a set of classes and their interrelationships.

CLASS INHERITANCE:
When a super class is extended by a sub class, a class inheritance relationship exists between them. The sub class inherits the methods and attributes of its super class. In Java, class inheritance is single inheritance. See interface inheritance for an alternative form of inheritance.

Object:
an object is an element (or instance) of a class; objects have the behaviors of their class. The object is the actual component of programs, while the class specifies how instances are created and how they behave.

An object is a software bundle of related variables and methods. Software objects are often used to model real-world objects you find in everyday life.

Method:
a method is an action which an object is able to perform.sending a message
sending a message to an object means asking the object to execute or invoke one of its methods.

A method is basically a function in C++, but unlike C++, they always belong to classes. That is, classes

Views
Provide a single view of data derived from one or more tables or views. The view is an alternative interface to the data, which is stored in the underlying table(s) that make up the view.

Sequences
Provide unique numbers for column values.

Stored procedures
Contain logical modules that can be called from programs.

Synonyms
Provide an alternative name for database objects.

Indexes
Provide faster access to table rows.

Database links
Provide links between distributed databases.

Packages

A package is a set of related functions and / or routines. Packages are used to group together PL/SQL code blocks which make up a common application or are attached to a single business function. Packages consist of a specification and a body. The package specification lists the public interfaces to the blocks within the package body. The package body contains the public and private PL/SQL blocks which make up the application, private blocks are not defined in the package specification and cannot be called by any routine other than one defined within the package body. The benefits of packages are that they improve the organisation of procedure and function blocks, allow you to update the blocks that make up the package body without affecting the specification (which is the object that users have rights to) and allow you to grant execute rights once instead of for each and every block.

Database Triggers

A trigger is PL/SQL code block attached and executed by an event which occurs to a database table. Triggers are implicitly invoked by DML commands. Triggers are stored as text and compiled at execute time, because of this it is wise not to include much code in them but to call out to previously stored procedures or packages as this will greatly improve performance (this only applies to pre v8i - thanks to Chenggan Duan for pointing that out). You may not use COMMIT, ROLLBACK and SAVEPOINT statements within trigger blocks. Remember that triggers may be executed thousands of times for a large update - they can seriously affect SQL execution performance

Procedures and Functions

A procedure or function is a named PL/SQL block - they are normally stored in the database within package specifications (which is a wrapper for a group of named blocks) but they may be stored on the database individually. The advantage of this is that when a block is placed on the database it is parsed at the time it is stored. When it is subsequently executed Oracle already has the block compiled and it is therefore much faster. It is also a good way of grouping application functionality together and exposing only function calls (not the code itself). It is possible to invoke a stored procedure or function from most Oracle tools including SQL *Plus. It is also possible to attach a block to a database or Form trigger.

Physical Database Design
What was the point in creating the logical data model? You want to create a database to store data about CDs. The data model is only an intermediate step along the way. Ultimately, you would like to end up with a MySQL or mSQL database where you can store data. How do you get there? Physical database design translates your logical data model into a set of SQL statements that define your MySQL or mSQL database.

Since MySQL and mSQL are relational database systems, it is relatively easy to translate from a logical data model, such as the one we described earlier, into a physical MySQL or mSQL database. Here are the rules for translation:

Entities become tables in the physical database.

Attributes become columns in the physical database. You have to choose an appropriate datatype for each of the columns.

Unique identifiers become columns that are not allowed to have NULLs. These are called primary keys in the physical database. You may also choose to create a unique index on the identifiers to enforce uniqueness. For your purposes, mSQL does not have a concept of a primary key. It simply has unique indices. This issue does not apply to MySQL.

Relationships are modeled as foreign keys. We will cover this later.

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1991- cgi- common gateway interface
1993- odbc- open databases connectivity
1995- isapi/odbc- visual basic and C++
1996- IDC- internet databases connectivity (sql)
1997- RDO -remote data object
1997- JDBC- java database connectivity
1999- OLE DB -Active Data Object
1999- PHP- Pre HTL processor

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Tools Used : Visual Studio.Net Beta 2, Oracle 8 database

How to use : Create a database table Emp with four data fields: EmpNo, EName, Sal, DeptNo

http://www.c-sharpcorner.com/Database/AccessOracleDBSK.asp

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DDL is Data Definition Language statements. Some examples:
CREATE - to create objects in the database
ALTER - alters the structure of the database
DROP - delete objects from the database
TRUNCATE - remove all records from a table, including all spaces allocated for the records are removed
COMMENT - add comments to the data dictionary
GRANT - gives user's access privileges to database
REVOKE - withdraw access privileges given with the GRANT command

DML is Data Manipulation Language statements. Some examples:

SELECT - retrieve data from the a database
INSERT - insert data into a table
UPDATE - updates existing data within a table
DELETE - deletes all records from a table, the space for the records remain
CALL - call a PL/SQL or Java subprogram
EXPLAIN PLAN - explain access path to data
LOCK TABLE - control concurrency

DCL is Data Control Language statements. Some examples:

COMMIT - save work done
SAVEPOINT - identify a point in a transaction to which you can later roll back
ROLLBACK - restore database to original since the last COMMIT
SET TRANSACTION - Change transaction options like what rollback segment to use

 

Creating the Standby Database Environment; Creating a Physical Standby Database; Understanding Logical Standby Databases; Disaster Recovery Setup on primary: 1) Create Service 2) Check Listener & Trasaction Files & Standby Control File 3) Copy Archive Logs 4) Name Standby DB 5) Recover DB ; Steps on secondary: 1) create service 2) Check Listener; On Primary Fail Safe; On Secondary Fail Safe; Verify --> Create DB groups.