Database Types

A database is a collection of related data, stored in an organised manner so that is can be retrieved later.

Many organisations use databases:

• Businesses
• Transport
• Search engines (Google, Yahoo, Bing)
• Government

Databases organise information into fields, records and tables.

• A Field is a property of an item
• A record is a collection of Fields
• Tables are collections of records

Each table in a databaes should have a primary key (keyfield). A primary key is a field which is unique (different) for every record in that table.

Each field in a database must also have a data type, which determines what sort of data can be stored in it.

Data types are a way of ensuring validation of data by only allowing data of a desired type.

Different data types (igcseict.info)

There are two main types of database: Flatfile & Relational

Read the following article which explains the differences between the two types.

• Types of database - Flatfile & Relational (igcseict.info)

Activity

Go to the TeachICT website and read through the whole section on database construction.

Visit the Introduction to Database Basics website and complete the interactive exercises. Have a go at the quiz at the end to see how much you have taken in.

Finally read some of the “geek girls” tutorials which explain the step by step process to creating a database: Databases:step-by-step guide to using databases.

Flat-file vs Relational - An Explanation

Relational Database

There may be many links between tables in a relational database.

These links (relationships) may be...

• one-to-one, e.g. products and barcodes in a supermarket.
• one-to-many, e.g. one video club member may loan a number of videos.
• many-to-many, e.g. pupils and teachers in a school.

Advantages of relational databases over flat-file databases:

• Data is more consistent.
• Each data item is stored only once. There is no danger of data being updated in one place and not in another.
• Data redundancy is eliminated, i.e., no data is unnecessarily duplicated thus wasting storage space.
• Information security has increased. The DBMS will ensure that only authorized users have access to the data.

Disadvantages:

• Setting up relational databases are more complex and require increased maintenance.
• If failure occurs, all applications using the data are affected.

NOTE: One thing that examiners always complain about in ITGS is student exam answers regarding databases. And so this guarantees that each year there are a number of database questions and usually you will need to explain a relational database and its merits.