Topic 6 - Databases

Relational Database - A group of tables linked together by primary and foreign keys

Data Warehouse - A database used to store an organisation's historical data which is used by an MIS to extract information to help managers make decisions

A large collection of archived data used for decision making

Example

Allows the company to see who has bought what items and why and then target them with special offers

Advantages

• It allows the company to store all the details of what it has sold to every customer
• Can compare information like the sickness data from other stores
• Can be mined
• Allows the organisation to store information about every sale
• Allows the organisation to see who has bought what items
• Allows the organisation to find the most popular product

Data Mining - Data mining is interrogating the data to find patterns in the data which is stored in the warehouse

Example/Advantage

Identification of customer needs - Virgin Media use data mining to segment and target customers most likely to buy new services or upgrades

Hierachy of Passwords limits users to various parts of the program. A receptionist would only have access to basic customer details whilst a manager would see all information on the customer account.

Independence - Data Independence is where the data and the applications used to access it are seperate. New systems can still use existing data.

Redundancy - Data redundancy is where you store an item of data more than once. This is wasteful because some data may need to be input twice and if data is changed in one it will need to be changed in the other

Consistency - Data consitency is the relationship between the input data, the processed data and the output data as well as other related data. If the system is working properly the data will be correct at each stage and is said to be consistent

• Hierachy of passwords - passwords to see seperate parts
• Storage of data separate to programs
• Access rights to parts of the program

Data Normalisation - A staged mathematical process which removes repeated groups of data and inconsistencies

Distributed Database - A distributed database has data stored on a number of computers at different locations but appears as one logical database

Advantages

• If one server fails, then the other servers can be used
• Easy to backup and copy data from one server to another
• Faster response to user queries of the database

Disadvantages

• Software more complex than a centralised database system
• If data is transferred it presents more of a security risk from hackers
• Increase costs owing to the use of expensive communication lines

• Add a link table
• Make it a one to many relationship

Data Redundancy - Where you store an item of data more than once

In a flat file database, details about information such as customer details will be duplicated. In a well designed relational database there should be no repeating attributes, no piece of data should be unnecessarily repeated

Data Integrity - The integrity of data is the correctness such as the extent to which it truthfully represents the original infromation. Truthful, Accuracy

One of the problems of maintaining intergrity arises when updating occurs and every record has to be changed in a flat file database, if one record was left unchanged the data would no longer be wholly correct. In a relational database you only have to change data in one table and all other references in any other application will automatically be changed

Data Consistency - Where the same data has exactly the same value and formating throughout

A date field could be stored in file as a text field but in another field as a date/time field and the data would be incompatible. In a relational database because the attributes of any one entity are contained within one file, there is no risk of the same attirbute being stored in a different format in a different file (spelling mistakes in names)

Issue: Viruses if linked to a local database

Solution: Use a firewall and anti-virus software

Issue: Problem hacking into local data. Computers are located on a number of hotel sites so it is important to ensure only authorsied users can access the system

Solution: Can be achieved by using passwords for authorised users, and regularly updating the passwords to increase the levels of security