Chapter 7 - Storing Organizational Information - Databases

Relationship Database Fundamentals

• Information is everywhere in an organization
• Information is stored in databases

          - Databases - maintains information about various types of objects (inventory), events (transactions),
                                  people (employees), and places (warehouses)

• Databases models include:

1. 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
2. Network database model - a flexible way of representing objects and their relationships
3. Relational database model - stores information in the form of logically related two-dimensional tables

HIERARCHICAL STRUCTURE

NETWORK STRUCTURE

Entities and Attributes

• Entity - a person, place, thing, transaction, or event about which information is stored

          - The rows in each table contain the entities
          - In Figure 7.1, CUSTOMER include Dave's Sub Shop and Pizza Palace entitties

• Attributes (fields, columns) - characteristics or properties of an entity class

          - The columns in each table contain the attributes
          - in Figure 7.1 attributes for CUSTOMER include Customer ID, Customer Name, Contact
            Name

Keys and Relationships

• Primary keys and foreign keys identify the various entity classes (tables) in the databases

          - 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 DATABASE ADVANTAGES

• Database advantages from a business perspective include:

  Increased flexibility

  Increased scalability and performance

  Reduced information redundancy

  Increased information integrity (quality)

  Increased information security

INCREASED FLEXIBILITY

• A well-designed database should:

  Handle changes quickly and easily

  Provide users with different views

  Have only one physical views

     Physical view – deals with the physical storage of information on a storage device

  Have multiple logical views

     Logical view – focuses on how users logically access information

  Example : a mail-order-buss-2 people view diff format (logical views) but same physical view

INCREASED SCALABILITY AND PERFORMANCE

• A database must scale to meet increased demand, while maintaining acceptable performance levels

  Scalability – refers to how well a system can adapt to increased demands

  Performance – measures how quickly a system performs a certain process or transaction

REDUCED INFORMATION REDUNDANCY

• Databases reduce information redundancy

       Redundancy – the duplication of information or storing the same information in multiple

                                    places

• Inconsistency is one of the primary problems with redundant information

INCREASE INFORMATION INTEGRITY (QUALITY)

• Information integrity - measures the quality of information
• Integrity constraint - rules that help ensure the quality of information

- Relational integrity constraint - rule that enforces basic and fundamental information-based constraints

- Example : Users cannot create an order for a nonexistent customer, provide a markup percentage that was negative etc.

- 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

- Example : Products returns are not accepted for fresh product 15 days after purchase

INCREASED INFORMATION SECURITY

-      Information is an organization asset and must be protected

-      Databases offer several security features including:

  Password – provides authentication of the user

  Access level – determines who has access to the different types of information

  Access control – determines types of user access, such as read-only access