This exercises will help you test your knowledge and skill of programming in Oracle database and practice the Oracle Quires concepts. You will start from basic exercises to more complex exercises. You should try to solve each problem by yourself. If you have any questions regarding to each problem, you can post them at our forum.

What Is Java?

Java is a computer programming language. 

It enables programmers to write computer instructions using English based commands, instead of having to write in numeric codes. It’s known as a “high-level” language because it can be read and written easily by humans. Like English, Java has a set of rules that determine how the instructions are written. These rules are known as its “syntax”. Once a program has been written, the high-level instructions are translated into numeric codes that computers can understand and execute.

Who Created Java?

In the early nineties, Java was created by a team led by James Gosling for Sun Micro systems. It was originally designed for use on digital mobile devices, such as cell phones. However, when Java 1.0 was released to the public in 1996, its main focus had shifted to use on the Internet.

It provided more interactivity with users by giving developers a way to produce animated webpages . Over the years it has evolved as a successful language for use both on and off the Internet. A decade later, it’s still an extremely popular language with over 6.5 million developers worldwide.

Why Choose Java?

Java was designed with a few key principles in mind:

·  Easy to Use: The fundamentals of Java came from a programming language called c++.Although c++ is a powerful language, it was felt to be too complex in its syntax, and inadequate for all of Java's requirements. Java built on, and improved the ideas of c++, to provide a programming language that was powerful and simple to use.

·  Reliability: Java needed to reduce the likelihood of fatal errors from programmer mistakes. With this in mind, object-oriented programming was introduced. Once data and its manipulation were packaged together in one place, it increased Java’s robustness.

·   Secure: As Java was originally targeting mobile devices that would be exchanging data over networks, it was built to include a high level of security. Java is probably the most secure programming language to date.

·   Platform Independent: Programs needed to work regardless of the machine they were being executed on. Java was written to be a portable language that doesn't care about the operating system or the hardware of the computer.

The team at Sun Micro systems were successful in combining these key principles, and Java's popularity can be traced to it being a robust, secure, easy to use, and portable language.

I guess the first question is really, "What is a database"?. A database is an organized collection of data. The data can be textual, like order or inventory data, or it can be pictures, programs or anything else that can be stored on a computer in binary form. A relational database stores the data in the form of tables and columns. A table is the category of data, like Employee, and the columns are information about the category, like name or address. 

Some databases have minimal feature sets and only store data, while others include programming languages, facilities and utilities to support enterprise-level applications like ERP and data warehousing. Oracle is the #1 database and has the most advanced feature set. 

Oracle is made up of a set of processes running in your operating system. These processes manage how data is stored and how it is accessed. I will cover these processes in detail in the future; but for now we just need to understand that Oracle is a program that is running in the background, maintaining your data for you and figuring out where it should go on your hard drive. 

In almost all relational databases, data is accessed through SQL, or Structured Query Language, and Oracle is no exception. SQL allows you to SELECT your data, INSERT new records, UPDATE existing records and DELETE records you want to get rid of. SQL can be embedded in other languages or you can run scripts of SQL directly against the database. 

PL/SQL is the procedural language extension to SQL. PL/SQL is a programming language like C, Java or Pascal. In the Oracle world, there is no better way to access your data from inside a program. SQL can be natively embedded in PL/SQL programs. I will be using both SQL and PL/SQL very heavily in my future articles. 

PL/SQL is a feature-rich language geared toward developing database applications. PL/SQL is the procedural language of the database, but it is also the procedural language for most of Oracle's tools. Programs that run inside the database are called stored procedures. These stored procedures are almost always PL/SQL, but can be written in Java. 

Some of Oracle's tools to access the database and create programs are: 

SQL*Plus has a command line interface. With it, you can access the database and write stored procedures, you can run SQL commands to retrieve data and you can run scripts of either SQL, PL/SQL or built-in SQL*Plus commands, or a mixture of those three things. 

Oracle Developer is a 4GL GUI application Builder. With Developer, you can create forms, reports, and graphics. Oracle*Forms and Oracle*Reports are two components of Oracle Developer. Earlier versions created client-server applications, but the more recent versions create web applications that run under the Oracle Application Server (OAS). OAS is a web-based application server sold by Oracle. OAS is licensed separately and is very expensive (as are its closed source competitors). The current version is OAS 10g. 

HTML DB is a fairly new application builder geared toward web development (added to the DB with release 9iR2). HTML DB does not need an application server. This tool runs from the database and can be presented to the web using the Apache web server that comes with the database. Since this is not an additional license, it provides a cheaper way to develop applications. Developer is a feature-rich thick client with all of the normal GUI widgets. HTML DB is HTML-based and is very thin and limited to the HTML provided widgets. 

Oracle Enterprise Manager (OEM) is the Enterprise GUI tool to manage the database. From this tool, you can perform any action in the database that is required. This tool is primarily used for administration but can also be provided to developers for application tuning and monitoring. In Oracle 10g, OEM also provides Grid control. 

There are also a lot of third party tools for accessing the database. For our purposes, our primary tool for data access will be SQL*Plus. In the future, I will cover creating applications with HTML DB and accessing your data with some choice third-party tools. 

How about Java? Java is the current hot language, especially on the web. I will also be covering Java in the database in future articles. Java is natively supported by Oracle.