Database Systems

Database Systems

1. Relational Database over Flat File

   • Data Consistency
     • The relationship between the input data, processed data and the output data. If the system is working properly the data will be correct at each stage so therefore consistent
   • Data Redundency
     • Where an item of data is stored more than once. It is wasteful to hold data in multiple files as if the data changes, it needs to be updated in each file location individually which is unnecessary and time consuming
   • Data Integrity
     • Making sure that the data is truthful and accurate. This issue can occur when updating a record in each location of a flat file database
   • Data Independence
     • The programme and the data are stored independently meaning that new applications can be created and used without having to change the data
   • Hierarchy of Passwords
     • Limits users to certain parts of the system. For example, a receptionist would only have access to a patient's details whereas a doctor would be able to change a patient's prescription
   • Access Rights
     • Only certain users can access and change data. A nurse would be able to view drug dosage but not change it
   • Normalisation
     • A staged mathematical process which removes repeated groups of data and inconsistencies
   • Primary Key
     • A unique figure which is used to identify a record. Other fields in the database rely on it
   • Foreign Key
     • A field of one table which is the primary key of another. It is used to establish relationships between tables

2. Relational Databases are more secure because...

   • Hierarchy of Passwords
     • Limits users to certain parts of the system. For example, a receptionist would only have access to a patient's details where as a doctor would have access to full medical history
   • Access Rights to the Program
     • Only certain people can access and change data. For example, a nurse would see prescription but could not change it
   • Storage of Data Separate to Program
     • The data and the program used to access it are separate as the data is stored elsewhere

3. Data Warehousing

   • Interrogating a database to find patterns in data which is stored in the warehouse
   • Uses
     • A company with a list of customers who regularly buy the same product can use this to target them with related offers
     • Useful "What If" scenarios from modelling
     • Analysis of sales patterns
     • Data can be processed into a report for use in decision making
   • An Example of Use
     • Identification of customer needs - A broadband company can use it to target customers more likely to buy a new product or upgrade

4. Database Management System

   • A method of managing the interface between the data stored and the programs which use the database
     • Uses
       • Data storage, retrieval and update
       • Creation and maintenance of a data dictionary
       • Backup and recovery of data
     • Advantages
       • Data independence from the program as data and program are stored seperately
       • Stored logically and structured
       • Data is stored centrally
     • Disadvantages
       • Costly to set up as expensive hardware and lots of staff expertise required to run the system
       • Security is essential because data stored centrally can be vulnerable

5. Structured Query Language

   • A data manipulation language used to perform more detailed searches or sorts

6. Distributed Databases

   • A distributed database has data stored on a number of computers at different locations but appears as a logical database
     • Advantages
       • If data is lost from one site, it can be restored from another local site
       • New locations can be added to the database without needing to rewrite the whole database
       • Easier to backup data from one server as there is a smaller amount of data
       • If one server goes down, the others can still function
     • Disadvantages
       • Software is more complex than a centralised system
       • Transfer of data from one location to another is a security risk as hackers could intercept
       • Heavy reliance on networks and communications which may not always be reliable
       • Increased costs owing to the use of expensive computer lines