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.

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.