DMS Flashcards
Data Model
Data model is a simple representation of complex, real-world data structure
Why data modeling is important
- Organises data for various users, such as the manager, system analyst, programmers
- Provides an abstraction that can be used to create the database
Constraints
- Constraint is a restriction placed on data
- It helps to ensure data integrity
- Constraint can only be restricted, eg income must be more than 0
Business Rules
- Business rules can define relationships, eg EMPLOYEE can only have 1 role
- Business rules can also define entities
Required Attributes
A required attribute must always contain a value in the row and cannot be left empty
How would you express a required attribute in your entity relationship diagram?
Write the attribute name in boldface
Computed Attribute
A computed attribute is an attribute that is computed from another attribute
What are the advantages of storing computed attributes on your database?
- Fast data access time
- Data value is readily available
Basic Building Blocks
Relationship, Attribute, Constraint, Entity (RACE)
4 Business Rules
Discovering, Reconciling, Documenting, Un-modellable
Associative (Composite) Entities
The associative entity bridges the two parent entities is composed of the primary key attributes of each parent entity
Primary Key (PK)
It serves as a unique identifier for each instance and ensures the integrity of an entity
Foreign Key
Foreign key works with the primary key to implement relationship in the relational model
