Definition of a Database and Database Management System WEEK EIGHT AND NINE

Definition of a Database and Database Management System

A database is defined as a collection of integrated data which are logically  related.

A batabase Management System (DBMS) sometimes called a Database Manager or Database System is a set of computer programs that controls the creation, organization, maintenance, and retrieval of data lo database stored in a computer. It allows the individuals or entities to access and use the data from database. An excellent database system helps the end user to easily access, use and stores the new data in a systematic way. It knows better the actual physical location of the data.

The most typical DBMS is a Relational Database Management System RDBMS). A newer kind of DBMS is the Object-oriented Database Management System (ODBMS). The DBMS are categorized according their data types and structure. It accepts the request for the data from an application program and instructs the operating system to transfer the appropriate data to the end user. A standard user and program interface is the structured Query Language (SQL).

Examples of Database Management System Software

The following are some database application software. They include IBM Dbase2. FoxBASE, Fox Pro, R Base, Super Base, Oracle and Microsoft Microsoft SQL Server, MySQL.

Database Basic Terminologies

Data is organised into characters, fields, records, files and databases. Computers encode data with “on” and “off” electrical states. Individual data •e represented by 0 (off) and 1 (on) and are called bits. Collection of  eight bits are organised into bytes representing characters. A bit is the t unit a data computer system can process at a time.

1. Character

A character is a single letter, number, special character such as a cm mi full stop, question mark etc.

2. Field

A field is a collection of characters that represent a single type of entity. Entities like price, name, address, town/city, state, country are all fields

3. Record

Record is a collection of related fields. All the information on a student result sheet is called a record. This includes, name, age, marks and posit! for each subject, and the result whether pass or fail. The information m driver’s license and identity card is a record.

4. File

A file is a collection of related records. The entire student's result issued out by a school in one academic year could be a result file. A file pertaining the salaries of a company is called a Payroll File.

8. Master file.

This is a complete file containing relatively permanent data such customer name and address, name of pupils in a school and their homo m contact addresses, their sex, blood group and so on.

2. Transaction file

This contains recent changes to records that will be used to update the master file. A file holding daily deposits, withdrawal and charges in a bank is an example of a transaction file

5. Database. A database is a collection of related files

The following illustrates how data is organized. In a school’s result register

Table

 We have four fields which are registration number, first name, initials, and result, while we have five records. Each column is a field, while each row is a record.

e key field

Our illustration shows the student's registration number as unique. No two students can have same registration number even if they have same name and initials. This distinctive field is called a key field. In the example able, the registration number is the key field.

The need/advantages for databases

For both individuals and organizations, there are many advantages of having abases:

(a) Sharing

organizations, information from one department can be readily shared 1 others.

(b) Security

Users  are given passwords or access only to the kind of information they Need. Thus, the payroll department may have access to employees' rates, but other department would not.

3. Fewer files

There are fewer files in a database environment. This is so because data redundancy is eliminated..

4. Data integrity

Data integrity is very high in a database environment. Changes made on any data in the organization are effected immediately.

5. Faster Response Time

Data that could have been stored in several files are integrated in a single database. Complex query can be handled much more quickly.

6. Lower Operating Cost

Since response time is faster more work can be done by users in less time.

Problems associated with databases

A major problem faced by an organization or individual implementing a database is cost. The cost are incurred in the following areas

1. Database Software

Database Management System Software is more expensive than other conventional software. Some could cost as much as $100,000 or more.

2. Hardware

It requires hardware with faster processing speed, memory and secondary storage and other auxiliary components.

3. Training

Users have to be trained for them to be able to use most Data Base Management System Software. This training cost a lot of money because they require specialized skills.

Database uses

Database offer great opportunities for productivity. Actually, in corporate libraries, electronic  database are now considered more valuable than books and journals. However, to maintain databases means users must make constant efforts  to keep them from being tampered with or used for the wrong purposes.

1. Business directories: they are used to provide addresses, financial and marketing information of products and trade brand names,
2. Demographic data: such are state and city statistics, current estimates on population and income, employment statistics, census ta and so on.
3. Business statistical information, such are financial information ding companies, market potential of certain retail store and business information

(4) Text databases, provides articles from business publications, press release reviews on companies and produces and so on.

Forms of databases

There are many forms of database organization. However for the purpose of we are going to deal with only three common. These are hierarchical, network and relational.

1. Hierarchical database:

In a hierarchical database, fields or records are structured in nodes. These points connected like the branches of a tree (an upside down nodes further down the system depends on the ones above like the hierarchy  of managers in a company. Each entry has a parent node, parent may have several child nodes. To find a particular field you have to start at the top with a parent and trace down the tree to the  child.

In this example the parent nodes are those labeled “departure” the airports from where planes take off. The first child in any airport is “arrival” from various flight destinations. The second child is “fight number” and the thud child is “passenger.”

The disadvantage with a hierarchical database is that if one parent node is  deleted, all the subordinate child nodes are also deleted. A child node cannot be added unless a parent node is added first. The limitation is that it is rigid in structure: one parent only per child and there is no relation' hip between the child nodes themselves.

2. Network Database: A network database has also a hierarchical arrangement of nodes; however each node may have more than mm parent node that is there is an additional connection between the p. urn it node and  the child node.

This example is in a school, a teacher can teach more than one course, and a student can take more than one course. This arrangement is more flexible and in more efficient than the hierarchical arrangement.

3. Relational database

Relational database is a type of database or database management system that stores information in tables—rows and columns of data—and conducts searches by using data in specified columns of one table to find additional data in another table. In a relational database, the rows of a table represent records (collections of information about separate items) and the columns represent fields (particular attributes of a record). In conducting searches, a relational database matches information from a field in one table with information in a corresponding field of another table to produce a third table that combines requested data from both tables.

This data is in the traffic office data base which shows all the cars registered in the city of Lagos. A row resembles a table showing the car number, name and address of the owner. Since no two cars have the same number, the car

number field is unique and it is called a key field. If the owner of the car commits an offence like over speeding or packing at an unauthorized place, the police can use his car number to trace him and subsequently prosecute him.

The most valuable feature of relational databases is that entries can be easily added, deleted and modified.

Database management system software

To illustrate how to use a database management system, Microsoft Access software will be used as our example.

Getting started with Microsoft access

To get to the Microsoft Access screen, you can achieve this in two ways.

The first way is to double click at the Microsoft Access shortcut icon on the desktop:

If the Microsoft Access icon is not placed on the desktop of your computer, the same result could be achieved using the following steps:

Step 1 Click on the start menu

Select -^ogrdrrii f_rom the pop-up menu

Diagram

Step 3:  Click on the Microsoft Access from the Programs sub-menu. A Microsoft/Access will be displayed on your screen.

Diagram

Task 1 Creating a database.

To create a new database we need to:

Click on the option Blank database... in the task pane that appears to the riqht of the screen.

Task 2 Closing a database.

A database can be closed in various ways:

Option One

Click on File in the menu bar, and then select the Close button.

Alternatively you can click on the Close button (^Sin the Database window. If we also want to close the Access session choose the option Exit from File menu or click on the close button in the title bar.

Task 3 Opening a database

There exist     different ways to  open  a   database.    However we will deal with

only two of     the options   which  are the   file    menu  bar and the toolbar

From the menu bar:                                                          

Go to the File menu.

Choose the Open... option.                                  

From the toolbar:

Which ever option you choose, the Open dialogue box will appear as shown below

Select the folder in which the database we want to open by double clicking on it

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