What is a Database?
A database is a persistent, organised store of related data.
- Data and structures are maintained when data handling applications are no longer running (they are held on some form of permanent medium such as a disk or flash memory).
- Data is stored in a very structured way, using tables, records and fields
- Easy for users and applications to add, delete, edit, search & manipulate data
- Individual items of data have a connection of some sort
- The data in a database is not just a haphazard collection of facts
Computerised Databases are better than Manual Databases (paper) because…
- data can be accessed by multiple users at the same time
- data can be queried / interrogated and resulting answers viewed
- data can be modified and made available to all end users quickly
- fewer errors in data processing
- data can be output to suit users’ needs (e.g. graphs, reports, forms), on screen or printed
A computerised database is a collection of related data stored in one or more computerised files in a manner that can be accessed by users or computer programs.
Most computerised databases are operational databases, meaning that data going into the database is used in real time to support the on-going activities of a business. A supermarket accounting system is an example: as items are sold, the inventory database is updated and the inventory information is made available to the sales staff.
Computers have the ability to store large amounts of data in a compact space and to process it speedily. Organisations of all sizes use databases to store, sort, interrogate and manage their data.
- Details of patients, doctors and treatments
- Stock control
- Manage and monitor sales, stock and staff etc
- Analyse performance of business / employees
- Monitor trends in customer purchases to identify market opportunities
Internet Search engines
- Google, Bing, Yahoo, etc.
- Powerful databases to collect the details of websites, search criteria etc.
A database can be viewed at three levels:
- The external view
- The conceptual view
- The physical view
Further details can be found here: Three levels acrhitecture DBS
This is what the user sees. It is a view that is designed to be useful for a particular job. Generally there will be a user-friendly interface that will allow the end-user to interact with the data contained within the database. The user does not need to be aware of the physical structure of the database, or how the data is stored within it.
This is concerned with how the data is organised. It has to do with the design of the tables, the types of data stored, validation rules used and how tables are linked. This is the equivalent of the ‘Design View’ when using MS Access.
- This is concerned with how the data is actually stored on the storage medium
- The designers and the users of the database are not concerned with this detail. It is looked after by the database software.