Learning question : Chapter 7

7.1   Define the fundamental concepts of the relational database model.

    A database maintains information about various types of object, event, people and place. In a hierarchical database model, information is organized into a tree-like structure that allows repeating information using parent/child relationships in such a way that it cannot have too many relationships.

   Hierarchical structure often cannot be used to relate to structure that exist in the real world. The network database model is flexible  way of representing objects and their relationships.

   Hierarchical model structure data as a tree of record s, with each record having one parent record and many children, the network model allows each record to have multiple parent and children records, forming a lattice structure. Relational database model is a type of database that stores information in the form of logically related two-dimensional tables.

   The primary concept of the relational database model entities, entity classes, attributes, key, and relationships. An entity in the relational database model is the person , place, things, transaction, or event about which information is stored. A table in the relational database model is the collection of the similar entities. Each entity class is stored in a different two-dimensional table. Attributes, also called fields or columns, are characteristics or properties of an entity class. Each specific entity in an entity class occupies one row in its respective table. The columns in the table contain the attributes.

   To manage and organize various entity classes within the relational database model, developers must identify primary keys and foreign keys and use them to create logical relationship. A primary keys is a field that uniquely identifies a given entity in a table. Primary keys are important because they provide a way of distinguishing each entity in a table.

A foreign key in the relational database model is a primary key of one table that appears as an attribute in another table and acts to provide a logical relationship between the two tables.

7.2   Evaluate the advantage of the relational database modal.

 

•            Increased flexibility.

           A good database can handle changes quickly and easily. Database provide flexibility in allowing each user to access the information in whatever way best suits his or her needs. The distinction between logical and physical views is important in understanding flexible database user views. The physical view of information deals with the physical storage of information on a storage device such as hard disk. The logical view of information focuses on how users logically access information to meet their particular business needs.

 

Example : A mail order business - one user might want a CRM report presented in                                                       alphabetical format, in which cast last name should appear before first name.

 

• Increased scalability and performance.

·         Only a database could “ scale “ to handle the massive volumes of information and the large numbers of users required for the successful launch website. Scalability refers to how well a system can adapt to increased demands. Performance measures how quickly a system performs a certain process or transaction.

Example : The official website of The American Family Immigration History Center, www.ellisisland.org , generated over 2.5 billion hits in its first year operation. The site offers easy access to immigration about people who entered American through the Port of New York and Ellis island between 1892 and 1924. The database contains over 25 million passenger names correlated to 3.5 million images of ships”.

• Reduced information redundancy.

·         Redundancy is the duplication of information, or storing the same information in multiple places. Redundant information occurs because organizations frequently capture and store the same information in multiple locations. The primary problem with redundant information is that it is often inconsistent, which make it difficult to determine which values are the most current or most accurate. Not having correct information is confusing and frustrating for employees and disruptive to an organization. One primary goal of a database is to eliminate information redundancy by recording each piece of information in only one place in database. Eliminating information redundancy saves space, ,make performing information updates easier, and improves information quality.

7.3   Compare relational integrity constraints and business- critical integrity constraints.

 

        Relational integrity constraints are rules that enforce basic and fundamental information-based constraints. While , business-critical integrity constraints enforce business rules vital to an organization’s success and often require more insight and knowledge that relational integrity constraints.

7.4   Describe the benefits of a data-driven website.

·         Development                    : Allows the website owner to make change any time without having to rely on a                                             developer or knowing HTML programming. Data-driven website enables                                                     updating with title or no training.

·         Content management        : A static website requires a programmer to make updates. This adds an                                                         unnecessary layer between the business and its web content,  which can lead to                                             misunderstandings and slow turnarounds for desired changes.

·         Future expendability        : Having a data-driven website enables the site to grow faster that would be                                                    possible with a static site. Changing the layout, displays, and functionality of the                                              site is easier with a data-driven solution.

·         Minimizing human error  : Even the most competent programmer charged with the task of maintaining many                                           pages will overlook things and make mistakes. This will lead to bugs and                                                       inconsistencies that can be time consuming and expensive to track down and fix.                                           Unfortunately, users who come across these bugs will likely become irritated and                                           may leave the site. A well-designed, data-driven website will have “error                                                       trapping” mechanisms to ensure that required information is filled out correctly and                                         that content is entered and displayed in correct format.

7.5  Describe the two primary methods for integrating information across multiple database

The first is to create forward  and backward integrations that link processes (and their underlying data databases) in the value chain.

 Forward integration takes information entered into a given system and sends it automatically to all downstream system and processes.

  Backward integration takes information entered into a given system and sends it to automatically to all upstream system and process.

An organization wants to build both forward and backward integration , which provide the flexibility to create , update , and delete information in any of systems. Most of organizations build only forward integration .  Building only forward integration implies that change in the initial system (sales) will result in changes occurring in all the other systems.

The second integration method builds a central repository for a particular type of information. Users can update and delete customer information only in the central customer information database. As users perform these tasks on the central customer information database  , integration automatically send the new and/or update customer information to the other systems. The other systems limit users to read only access of the customer information stored in them. Again, this method does not eliminate redundancy but it does ensure consistency of the information among multiple systems.