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 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
Entity and Attribute
- Entity - A person , place, thing, transaction, or event about which information is stored.
- Attributes (field, columns) - characteristics or properties of an entity class.
Keys and Relationships
Primary keys and foreign keys identify the various entity classes (tables) in the database
- Primary key - a field (or group of fields) that uniquely identifys a given entity in a table.
- Foreign key - a primary 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 integrity (quality)
- Increased information redundancy
- Increased information security
A well-designed database should:
- Handle changes quickly and easily
- Provide users with different views
- Have only physical view - deals with the physical storage of information on a storage device
- Have multiple logical 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 tp increased demands
- Performance : measures how quickly a system performs a certain process or transaction
Reduced Information Redundancy
- Databases reduce information redundancy - The duplication of information or storing the same information in the multiple places.
- Inconsistency is one of the primary problems with redundant information.
Increased Information Integrity (Quality)
- Information integrity : measures the quality of information
- Integrity constraint : rules that help ensure the quality of information