What is a database?
Introduction
Databases are everywhere! They are used to store details of pupils in your school, health records are increasingly held in a database and driving licence details are held by the DVLC. The police keep records of crimes and criminals, shops keep details of what they have for sale and what they have sold and the Government keeps details about its citizens, for example, for tax reasons. In fact, the more you look, the more you find databases in use. As they are so important and impact in our lives every day, it is reasonable that we should know all about them if we are doing a Computing course!
What is a database?
When you look inside any filing cabinet, you will find that it typically holds records e.g. patient records in a hospital. Each 'record' might be a single piece of paper or a folder of pieces of paper. Each record holds the data about a particular person you want to keep details about. The records are organised, sometimes in alphabetical order using each patient's surname from A - Z (ascending order) or perhaps Z - A (descending order) or perhaps by some other piece of data, such as who was born first or postcode or patient number and so on. Sometimes, you want to search through the database and get back a single record, or a set of records e.g. everyone who has had an operation in the last month. You might want to do other things to your filing cabinet of records, such as sort the records in a different order, or add, delete or amend a record.
Our filing cabinet of records is a database and for a long time, this was the only kind of database that could be used to store, organise and search data. There are problems with this kind of manual system. It is easy to lose a record by misfiling it in the wrong place. It is hard to take a million hospital records and put them in a different order, or search through all of the records for those that meet a certain set of criteria. When computers came along, so did software that allowed someone to make and use computerised databases. Suddenly, all the hard jobs associated with manual systems became easy any now anyone can make and use a database! You can set up a new database structure, define what records you want to keep and what data has to be in the records and then you can sort the records, search the records and do lots of other jobs using the software tools provided.
Persistent organised store of data
So we know that a database is an organised collection of data items and the links between the data items. What usually happens with databases is that you set up your database of data on the one hand, and then quite separately, use software applications that can access the data and sort and search it on the other hand. The data items are organised into a database structure, which is completely separate from the applications that use them. You might ask why you would do this. Well, with a bit of organising using a special piece of software known as a Database Management System (DBMS), different applications can get access to the same database by keeping it separate from the applications that use it.
We often use the word 'persistent' when talking about databases. Even though an application may not actually be searching through the data or doing something else with the data, the database is still there, it still exists.