Information and Communication Technology English Version chapter 6: Database Management System

Chapter Six

Database Management System

Figure: Data aggregation, collection and processing in an organized way is a huge challenge for the current world

Nowadays, almost everything we do, buy or get, can be done through the internet. We buy products online, pay our bills online, we get our banking services and healthcare services online, and almost all of our entertainment sources are now online. This vast amount of online resources need to be stored somewhere. Once we used to store our information only on papers and books. But now our information is handled by database management system. This surely made our life a lot easier but it has a certain number of challenges. Sometimes database systems can not be extended large enough, or data can not be retrieved fast enough or the security is compromised from cyber attacks. So the computer scientists are still working tirelessly on database management system with the goal of making it faster, more powerful and more secured. The students will get a basic overview of the database management system from this chapter.

After completing this chapter students can

• Explain the concepts behind a database management system
• Describe the work process of a database management system
• Learn the concepts of relational database management system
• Know the characteristics of a relational database management system
• Explain a total relational database management system
• Explain the concepts of database security
• Learn the importance of database security
• Explain the usefulness of data encryption
• Learn about the different ways to encrypt data practical
• Can create a database

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6.1 Database Management

Database management systems are a type of software that acts as an interface (maintaining a two-way connection) between the user and the database. The user requests the DBMS to perform various operations, and the DBMS, responding to the requests by the user and acting on the database provides the user with the required data. We work with information and data in every walk of our lives. In educational institutions, businesses, offices and even in our own residence too. Educational institutions are prime examples of multiple facets of database management system usage. Student admission, making a class routine, attendance, exam schedule, result tabulation and storage, tuition fee collection all of these activities need a lot of data to be computed and stored. For many ages, mankind has been keeping track of data with pen and paper. The advent of computers has made life a lot easier for us. Computers can store an enormous amount of information and process a lot of data at once, men with pen and papers can not compete with that. So we developed a bunch of software that uses this data storage and processing capabilities of computers and created database management systems.

Let’s say for illness and other reasons a student remained absent frequently from his classes. His parents wanted to know what classes their child missed in the last 3 months. In the old days, the parent would have to go physically to the school, meet with all of the teachers that are in charge of the classes, get the attendance book from all of them and check manually whether his child was absent from their classes in the last 3 months or not. This is a very tedious process and will take a lot of time. But if that school uses a database management system to feed all of the necessary and relevant data of the school, this information can be processed in a matter of seconds. Database is the system that stores the data and the system that operates the database is called the database management system.

6.1.1 Computer Memory and Files

We previously mentioned in an earlier chapter that, whenever a computer program works with some data, it puts them into a volatile memory. This volatile memory is known as the RAM. If the computer is shut down, the RAM is wiped clean. The RAM data can also be wiped clean if you shut down the running program. So store the necessary data we need to transfer them to a more permanent memory like the hard disk drive. The data in the hard disk drive is accessed through a system known as the file system. For example, we can create a text file and write some texts in it then save and close the file. Even if we shut down the computer and when we restart and open the file, we will find the previous written texts there in the file.

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When people first started using the computer for storing data, they used different programs that would write the data into files. To modify the data in those files or to process the data in those files, it would require different programs. Let’s say we have an address book program where different persons' names, address, phone numbers are stored. If we need to, we can search and locate those information. Now we need a program that will let us perform data entry operations so we can enter new data. We need another program to search and find existing data. If the requirement suggests that we need to store the user's email address alongside other information, we need to rewrite the data entry and search programs. Requirements may arise so that we need to search with user names alongside their email addresses, we need to rewrite all of the programs. We can see that using only a file system, data management becomes a tedious and time consuming matter for the programmers. Database management systems make this work a lot easier to handle.

6.1.2 Database

The main function of DBMS is to create a database, add and remove new records, update records, ensure data security, prevent data duplication and generate reports.In a literal sense, a database is a collection of data. But in the realm of computer science, a database is a software that can store a huge amount of data, that can search and find data, create, edit and delete data and process the data. Database management system is a program or a software that manages and controls a database.

In a broader sense a database can be of two types - relational database and NoSQL. The concept of relational databases was developed almost 50 years ago but it is still relevant and the most widely used database system. NOSQL database is relatively a new concept, its application in web based application is growing day by day. There are some limitations for which the NoSQL database isn't still widely used for all types of applications.

6.2 Relational Database

In relational databases, data is stored in one or multiple tables. Some tables can have relations between them. For example, a school database can have information on that school's teachers and students. Exam results, class attendance, class routines can also be stored in that database. Same type of information are usually put into the same table. For the information of a teacher we can have a teacher table and for the information of student we can have a student table. Exam results can be kept in a result table and the result table will have a relation with the student table so we can retrieve a student's personal information and result information in one move. All of these are compiled in a school database.

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A database table has two parts - table header and table body. A table header contains the column names, types of data and the table body contains the actual data. Each row of the table contains a certain data. Firstly we must decide on what data and what types of data we will store inside a table. Let’s say a table of a student can contain name, roll number, class, section, parents name, contact number, address etc.

Data types can be of different sorts. As we have seen, C programming has different data types, similarly a relational database has some defined data types. Different database developers define data types differently but some data types are common for every database, like - text, integer, decimal numbers, date etc.

Now let us look at an example of a database table.

Table name: Student

The first row of the student’s table is the header of the table. Each cell of this row is a column and each column has a data type. Student’s name is a name of a column and it’s data type is text. Every cell of this column will contain text type data and it will contain a student name. Every row below the header contains a certain student’s information. The second row contains the information of a student’s named Mijanur Rahman, his roll number, class, section, and parent's information. Similarly each row will contain a student’s information, one row will never contain more than one student's information. Each row of the table is also known as records. Each cell in the table is known as fields.

Some of the most popular relational database systems in the world are Oracle, MySQL, Microsoft SQL Server, PostgreSQL, Microsoft Access and SQLite. Among these, MySQL, PostgreSQL and SQLite are free and open source databases. This means you do not need to pay to use these databases and their source codes are open for all.

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