1) Define the fundamental concepts of the relational database model.
A database can be understood as a collection of related files. How those
files are related depends on the model used. Early models included the
hierarchical model (where files are related in a parent/child manner,
with each child file having at most one parent file), and the network
model (where files are related as owners and members, similar to the
network model except that each member file can have more than one
owner).
The relational database model was a huge step forward, as it allowed files to be related by means of a common field. In order to relate any two files, they simply need to have a common field, which makes the model extremely flexible.
The relational database model was a huge step forward, as it allowed files to be related by means of a common field. In order to relate any two files, they simply need to have a common field, which makes the model extremely flexible.
2) Evaluate the advantages of the relational database model.
The popularity of the relational database
approach has been apart from access of availability of a large variety
of products also because it has certain inherent advantages.
1. Ease of use: The revision of any information as tables consisting of rows and columns is quite natural and therefore even first time users find it attractive.
2. Flexibility: Different tables from which information has to be linked and extracted can be easily manipulated by operators such as project and join to give information in the form in which it is desired.
3. Precision: The usage of relational algebra and relational calculus in the manipulation of he relations between the tables ensures that there is no ambiguity, which may otherwise arise in establishing the linkages in a complicated network type database.
4. Security: Security control and authorization can also be implemented more easily by moving sensitive attributes in a given table into a separate relation with its own authorization controls. If authorization requirement permits, a particular attribute could be joined back with others to enable full information retrieval.
5. Data Independence: Data independence is achieved more easily with normalization structure used in a relational database than in the more complicated tree or network structure.
1. Ease of use: The revision of any information as tables consisting of rows and columns is quite natural and therefore even first time users find it attractive.
2. Flexibility: Different tables from which information has to be linked and extracted can be easily manipulated by operators such as project and join to give information in the form in which it is desired.
3. Precision: The usage of relational algebra and relational calculus in the manipulation of he relations between the tables ensures that there is no ambiguity, which may otherwise arise in establishing the linkages in a complicated network type database.
4. Security: Security control and authorization can also be implemented more easily by moving sensitive attributes in a given table into a separate relation with its own authorization controls. If authorization requirement permits, a particular attribute could be joined back with others to enable full information retrieval.
5. Data Independence: Data independence is achieved more easily with normalization structure used in a relational database than in the more complicated tree or network structure.
6. Data Manipulation Language: The possibility
of responding to ad-hoc query by means of a language based on
relational algebra and relational calculus is easy in the relational database
approach. For data organized in other structure the query language
either becomes complex or extremely limited in its capabilities.
3) compare relational integrity constraints and business- critical integrity constraints
There
are two types of integrity constraints: (1) relational integrity
constraints and (2) business-critical integrity constraints.
Relational integrity constraints are rules that enforce basic and fundamental information-based constraints.
Business-critical integrity constraints
enforce business rules vital to an organization’s success and often
require more insight and knowledge than relational integrity
constraints.
4) describe the benefits of a data- driven website
the benefits of a data-driven websites is .....
- Enabling many (potentially non-technical) users to provide content for the website. Users can publish articles on the website without needing to FTP them to a web server.
- Shopping cart
- You can provide advanced search functionality that enables users to filter the results based on a given field. They can then sort those results by a field - say "Price" or "Date".
- Customized homepage
- You can allow your users to perform tasks such as registering for a newsletter, post questions to your forums, provide comments on a blog, update their profile, etc.
- Integration with corporate applications such as CRM systems, HR systems etc
- Much more
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