4.3.6 - Database Systems - Database Systems
Teacher recommended
?- Created by: Annie
- Created on: 05-05-13 20:18
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- Database Systems
- Data security
- In a flat file database, the entire file will have the same (or no) security
- A relational database can have different security levels on each of the tables
- Different groups of users can have rights based upon read/write/add permissions
- Employers can view/amend data relevant to their job role
- Such groups will often be based upon a hierarchy with managers having fuller access than lower level employees
- Data warehousing
- Data is used to support organisational decision making
- Data is available for analysis
- Enables predictions of future sales to be much more accurate
- Comparisons between regional sales of different products
- Examples would include customer transaction details
- For banks and supermarkets
- Data is non-volatile and time invariant
- Doesn't change
- The idea that data for an organisation is stored in a central location
- Large organisations have huge amounts of data - hence the term warehouse
- Data mining
- Using data stored to extract useful information
- It is a speculative process and investigates potential patterns
- There is the presumption that dormant within the data are undiscovered patterns, groupings, sequences or associations
- Software uses complex algorithms
- Data of value can be processed into a report to help decision making
- Flat file database
- One or more tables with no relation between them
- Database management system (DBMS)
- A DBMS is used to manage the data held in the database and provide an effective connection to other applications which use data
- Data to be queried and searched
- New data to be added to tables
- Updates to be made to large datasets
- Security of the data to be maintained
- Data exchange with other applications
- Applications and the DBMS can be updated independently of each other
- Referential integrity, validation (etc.) are used to maintain the integrity of the data
- Microsoft Access is a Database Management System
- Difference between MIS: Different Information outputs such as graphs, charts etc. for decision making purposes
- A DBMS is used to manage the data held in the database and provide an effective connection to other applications which use data
- Query Languages (SQL)
- Standard query language is used to flexibly search all databases
- Access includes a graphical query interface that makes it easier for users to search a database
- Knowing SQL means much more intricate searches can be created - ideal for data mining
- Distributed Databases
- Large organisations frequently store data in a range of locations, typically based upon where the data is being used or accessed most
- To maintain a high speed response!
- A distributed database allows the user to access the data as if it is in one location
- Access speeds may be slower if some/all the searched data is located in different locations
- Data is controlled under the control of a single DBMS
- A customer looking for a certain item may go into a shop -
- The employee can search within the store database
- If no findings, can search other store databases so the customer can find it
- Advantages
- All data in an organisation can be accessible through a single DBMS
- Complex data mining is possible from a single query
- Disadvantages
- Complex and costly to set up
- Increased security risks
- System relies upon communication links
- If these fail, so does the system
- Various differences at each shop effecting communication
- e.g. Road works hitting a cable
- Large organisations frequently store data in a range of locations, typically based upon where the data is being used or accessed most
- Data Dictionary
- Vital piece of database development documentation
- It provides details of the design should the database have to be upgraded in the future
- Makes updates easier without disrupting company operations more than necessary
- Useful if original database designers are no longer around
- Shows data
- Validation Used
- Field lengths
- Relationships
- Data types
- Key fields
- Field names
- Data security
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