Week 2 Flashcards
Why is data modelling important?
Data modelling is important because it provides:
- Simple representation of complex data
structure and an overall view of the
database - Facilitates communication among database
designer, application programmer and the
end users.
What is a Data Model?
A data model is the blueprint of the database. It is basically the graphical representation of a complex data structure. Is known as an entity relationship diagram (ERD)
What are the basic building blocks of a database model?
- Entity: anything for which we intend to collect data
- Attribute: Characteristic of an entity
- Relationship: describes an association among entities
- Constraint: A restriction placed on the data
What are the different types of relationships among entities?
The different types of relationships are:
- One-to-many (1:M) relationship
- Many-to-many (M:N or M:M) relationship
- One-to-one (1:1) relationship
What are business rules?
Business rules are brief, precise, and unambiguous descriptions of policies, procedures, or principles within a specific organization
What are the reasons for identifying and documenting business rules?
Reasons for identifying and documenting business rules are they:
- Help standardize company’s view of data
- Are a communications tool between users and designers
- Allow designer to:
- Understand the nature, role, scope of data, and business processes
- Develop appropriate relationship participation rules and constraints
- Create an accurate data model
What are the general rules for translating business rules into database models?
- Generally, nouns translate into entities
- Generally, verbs translate into
relationships among entities - Relationships are bi-directional
What are the naming conventions used when creating an ERD?
- Entity names are required to be descriptive of the objects in the business environment and use terminology that is familiar to the users.
- Attribute names are required to be descriptive of the data represented by the attribute.
What is a Relational Database Model (RDB)?
An RDB is a collection of tables for data storage where tables are linked by sharing common entity characteristics (common column)
What are the advantages of the Relational Database model?
The advantages of the relational database model are:
- Structural independence
- Improved conceptual simplicity
- Easier database design
- Ad hoc query capability with SQL
- Powerful database management system
What are the disadvantages of a Relational Database Model?
The disadvantages of a relational database model are:
- substantial hardware and system software overhead
- Poor design and implementation is made easily
- May promote islands of information problems
What is a Super Key?
A super key is an attribute or combination of attributes that uniquely identifies any given row (not necessary to be minimal)
What is a Candidate Key?
A candidate key is a possible primary key. Some tables may have multiple candidate keys. A candidate key is a minimal super key (eligible as a primary key)
