Relational Database Fundamentals
Information is stored in databases.
* Database – maintains information about various types of objects (inventory), events (transactions), people (employees), and places (warehouses).
* Database models include :
- Hierarchical database model – information is organized into a tree-like structure (using parent/child relationships) in such a way that it cannot have too many relationships.
- Network database model – a flexible way of representing objects and their relationships.
- Relational database model – stores information in the form of logically related two-dimensional tables.
Entities and Attributes
Entity – a person, place, thing, transaction, or event about which information is stored. (The rows in each table contain the entities)
Attributes (fields, columns) – characteristics or properties of an entity class. (The columns in each table contain the attributes.)
Primary keys and foreign keys identify the various entity classes (tables) in the database.
Primary key – a field (or group of fields) that uniquely identifies a given entity in a table
Foreign key – a primary key of one table that appears an attribute in another table and acts to provide a logical relationship among the two tables.
Relational Databases Advantages
1. Increased flexibility
a) Handle changes quickly and easily.
b) Provide users with different views.
c) Have only one physical view.
i. Physical view – deals with the physical storage of information on a storage device e.g. hard disk.
d) Have multiple logical views.
ii. Logical view – focuses on how users logically access information.
Eg: a mail-order buss- 2 people view diff format (logical views) but same physical view
2. Increased scalability and performance
a) A database must scale to meet increased demand, while maintaining acceptable performance levels.
i. Scalability – refers to how well a system can adapt to increased demands.
ii. Performance – measures how quickly a system performs a certain process or transaction.
3. Reduced information redundancy
a) Databases reduce information redundancy.
i. Redundancy – the duplication of information or storing the same information in multiple places
b) Inconsistency is one of the primary problems with redundant information - difficult to decide which is most current and most accurate.
4. Increase information integrity (quality)
a) Information integrity – measures the quality of information.
b) Integrity constraint – rules that help ensure the quality of information.
i. Relational integrity constraint - rule that enforces basic and fundamental information-based constraints.
ii. Eg. Users cannot create an order for a nonexistent customer ; An order cannot be shipped without an address.
iii. Business-critical integrity constraint -rule that enforce business rules vital to an organization’s success and often require more insight and knowledge than relational integrity constraints.
iv. Eg. Product returns are not accepted for fresh product 15 days after purchase; A discount maximum of 20 percent.
5.Increased information security
a) Information is an organizational asset and must be protected.
b) Databases offer several security features including :
i. Password – provides authentication of the user.
ii. Access level – determines who has access to the different types of information.
iii. Access control – determines types of user access, such as read-only access
Databases Management Systems
Database management systems (DBMS) is a software through which users and application programs interact with a database.
Data-driven Web Sites
Data-driven Web sites is an interactive Web site kept constantly updated and relevant to the needs of its customers through the use of a database.
The advantages of data-driven web site :
1) Development: Allows the Web site owner to make changes any time—all without having to rely on a developer or knowing HTML programming.
2) Content management: A static Web site 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.
3) Future expandability: Having a data-driven Web site enables the site to grow faster than would be possible with a static site. Changing the layout, displays, and functionality of the site (adding more features and sections) is easier with a data-driven solution.
4) Minimizing human error: A well-designed, data-driven Web site will have ”error trapping” mechanisms to ensure that required information is filled out correctly and that content is entered and displayed in its correct format.
5) Cutting production and update costs: A data-driven Web site can be updated and ”published” by any competent data entry or administrative person. In addition to being convenient and more affordable, changes and updates will take a fraction of the time that they would with a static site.
6) More efficient: With a data-driven solution, the system keeps track of the templates, so users do not have to.
7) Improved Stability: With a data-driven Web site, there is peace of mind, knowing the content is never lost—even if your programmer is.
Integrating Information among Multiple Databases
Integration allows separate systems to communicate directly with each other.
A. Forward integration – takes information entered into a given system and sends it automatically to all downstream systems and processes.
B. Backward integration – takes information entered into a given system and sends it automatically to all upstream systems and processes.
Building a central repository specifically for integrated information.
Without integration, an organization will:
* Spend considerable time entering the same info in multiple system.
* Suffer from the low quality and inconsistency typically embedded in redundant information.
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