Presentation on theme: "Content 15.1 Basic features Types of database Data structures 15.2 Creating a database Screen layout Entering data Editing data 15.3 Displaying data Searching."— Presentation transcript:
Content 15.1 Basic features Types of database Data structures 15.2 Creating a database Screen layout Entering data Editing data 15.3 Displaying data Searching Queries Sorting records 15.4 Create and print reports Creating a report Printing a report DataBases
Outcomes By studying this chapter you should be able to: create a database; search and sort records in a database; display data using a selective query; design a variety of report formats to meet different needs. This chapter will help you to become a competent user of a database. It examines the basic features of databases and how to create a database. You will learn how to construct a query, how to create a report and how to modify a database
A database is an organised collection of data. People have used databases for many years, long before the advent of the computer. The telephone book is a database which is arranged alphabetically by family name. Another example is the traditional office filing cabinet. In recent years, computerised databases have been developed. There are three main reasons for this: Computers are ideal tools for searching a large amount of data, quickly and accurately. A computerised database allows cross-referencing, a feature that is very complicated on paper databases. Computerised databases can be updated without having to type all the data. A huge amount of information can be stored on disks, revised and arranged as appropriate. A computerised database can divide the data into sections for particular applications.
Databases are accessed by a database management system (DBMS), a software package that builds, maintains and provides access to a database (see Figure 15.1). The DBMS allows you to choose which data is required and how to display that information in a meaningful way. Before the advent of DBMS there was no alternative but to create a database using high level languages like COBOL, FORTRAN or C. Now, if a customised database is not required, a database can be created within a short amount of time using a DBMS.
Types of database A flat file database is the simplest type of database. All its data is contained in one file. Flat file databases are used for simple structured tasks such as storing personal names and address details. We examine flat file databases in this book. Databases can also be classified as a prepared database or an empty database. A prepared database (closed database) contains information about a specific subject. Its data can be accessed and read, but not changed. For example, a census on CD-ROM is a prepared database. An empty database
Data structures Data is the raw facts put into the computer system, such as text and numbers. This data is then processed by the computer. When the data has been ordered and given some meaning, it is called information. It is the result of work on the computer and depends on the data entered. Data is stored in data structures called files, records, fields and characters. To illustrate these data structures, consider the telephone book as an example of a database (see Figure 15.2). A file is a block of data. When you have done some work on the computer it is stored in a file. The L-Z telephone book would represent a file. A file in a database is divided into a set of related records
A record is a collection of facts about one specific entry in a database. Information about a person in the telephone book is a record. A record is divided into one or more related fields. A field is a specific piece of data. The family name, address and telephone number in the telephone book are fields. A field is also known as a data item or category and is made up of characters. A character is the smallest unit of data that people can handle and includes letters, numerals and special symbols.
1. Copy and complete the following sentences. Ais an organised collection of data. A flat file database is thetype of database. A prepared database containsabout a specific subject. An empty database allows data to be entered and (e)is the raw facts put into the computer system, such as text and numbers. Ain a database is divided into a set of related records. Ais a collection of facts about one specific entry in a database. A record is divided into one or more related Ais the smallest unit of data that people can handle. 2. Why have computerised databases developed in recent years? 3. How do you access a database? 4. What is the purpose of flat file databases? 5. Explain the difference between a prepared database and an empty database. 6. List the four data structures used in databases.