Relational Databases Fundamentals
- Information is stored in databases.
Databases MODULES include :
- Hierarchical databases model - information is organized into a tree-like structure (using parent/child relationship) in such a way that it cannot have too many relationships.
- Network databases model - a flexible way of representing objects and their relationships.
- Relational databases model - stores information in the form of logically related two-dimensional tables.
ENTITIES AND ATTRIBUTES
Entity - is a person, place, thing, transaction or event about which information is stored.
Example : The rows in each table contain the entities.
Attributes - Characteristics of properties of an entity class.
- The column in each table contain the attributes.
KEYS & RELATIONSHIPS
- Primary keys and foreign keys identify the various entity classes in the databases.
1) Primary Key = A field that uniquely identifies a given entity in a table.
2) 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
Database advantages from a business perspective include:
Increase Flexibility
A well-designed database should:
- Handle changes quickly and easily
- Provide users with different views
- Have only one physical view.
physical view = deals with the physical storage of information on a storage device. e.g. hard disk. - Have multiple logical view.
logical view = focuses on how users logically access information. e.g. A mail-order buss-2 people view different format but same physical view.
Increase scaleability and performance
A database must be scale to meet increased demand, while maintaining acceptable performance levels.
a) Scalability - refers to how well a system can adept to increased demands.
b) Performance - measures how quickly system performs a certain process or transaction.
Reduce information redundancy
Database reduced information redundancy.
a) Redundancy - the duplication of information or storing the same information in multiple places.
Inconsistency is one of the primary problems with redundant information-difficult to decide which is most current and most accurate.
Increase information integrity
a) information integrity - measure the quality of information.
b) integrity constraint - rules that help ensure the quality of information.
Relational information integrity
= rule that enforces basic and fundamental information-based constraints.
e.g. Users cannot create and order for a nonexistent customer, provide a markup percentage that was negative.
Business-critical integrity constraint
=rule that enforce business rules vital to an organization's success and often require move insight and knowledge than relational integrity constraints.
Increase information security
Information is an organizational asset and must be protected.
Database offer several security features including:
a) Password = provides authentication of the user.
b) Access level = determine who has access to the different types of information.
c) Access control = determine types of user access such as read-only access.
Database management system (DBMS) is a software through which users and application programs interact with a database.
Data-driven web sites = an interactive web site kept constantly updated and relevant to the needed of its customers through the use of a database.
Data-driven web sites advantages:
1) Development
2) Content Management
3) Future Expandability
4) More Efficient
5) Improve Stability
6) Minimizing Human Error
7) Cutting production and Update Costs
END OF CHAPTER 7.. THANK YOUUUU...
No comments:
Post a Comment