Topic 6 Database systems Flashcards
Relational database
A large collection of data items stored in tables containing links between the tables so that the data can be accessed in many different ways and by a range of different programs.
Advantages of Relational Databases over the ‘Flat File’ system
Data consistency
Data integrity
Data Redundancy
Data Independence
Data Consistency
Using one file to hold a central pool of data
Data Integrity
The correctness of data. Truthful and accurate
Data Redundancy
Where you store the same item of data multiple times.
Data Independence
The data and the programs used to access the data are separate.
Normalisation
A staged process which removes repeated groups of data and inconsistencies
Data warehouse
A large amount of data stored together usually in a single location for further processing
Data mining
Interrogating the data.
Distributed database
A database where data is stored at different locations but appears as one logical database.
Primary keys/Foreign keys
A field used to uniquely define a a particular row in a table
The primary key on the one side of the relationship becomes the foreign key on the many side.
Distributed Database Advantages (3)
Data is not stored in one location, so less risk of it being inaccessible.
Faster response to user queries of the database
Easy to backup and copy data from one server to another.
Distributed Database Disadvantage (3)
They are more complex so it is more expensive to install/maintain.
Easier for hackers to steal data
If data is stored and updated in more than one place there is an increased chance of data inconsistency
Data Warehouse Advantage
Allows organisations to see who bought what and when they did it.
Data Mining Advantage
See patterns in the data e.g. Virgin media use it to target customer that are most likely to buy new services
