Lesson 2 - Week 3-4 Flashcards
Database Designing Process
- Requirement collection
- Conceptual schema
- Basic data model operations
- Actual implementation of database
- Physical database design
____ models help the designer in describing data at the logical level. This type of model provides flexible capabilities which let constraints be clearly defined.
Object-based logical models
____ models are used to state the general logical structure of the database and to offer an advanced description of the implementation.
Record-based logical models
____ models describe data at the lowest level. Although seldom used, they capture the features of implementing a database-system.
Physical data models
____ uses a group of tables to indicate relationships among those data. Each table contains several columns, and each of them owns a unique name.
Relational Model
Data is shown in groups of records in a network database. Relationships are represented by links. The collection of records is structured as a group of arbitrary graphs.
Network Model
The ____ is similar to the network model as records and links represent data and relationships among data respectively.
hierarchical model
Proposed by Peter P. Chen in 1976; identifies that the real world is composed of entities and their relationships.
Entity- Relationship Model
____ is a visual representation of data that describes how data is related to each other.
Entity Relationship Diagram
An ____ is any visible object which stores information and can be a person, place, thing, event or a concept; An ____ may be physical or abstract.
Entity
____ are the properties of entities which we can use to identify them.
Attributes
Types of Attributes
- Key or non-key
- Required or optional
- Simple or composite
- Single-valued and multi-valued
- Stored, Coded or derived
An ____ is the structure for the set of entities that share the same structure
entity type
the individual entities of a particular entity type are collectively called ____.
entity set
Each attribute of an entity type is associated with a ____.
value set
This value set is also called ____.
domain
The ____ of an attribute is the collection of all possible values an attribute can have.
Domain
Any linkage or connection between different entities indicated by a verb is called a ____.
Relationship
Each relationship has:
Name, Degree, Cardinality
____ refers to the number of entities related to the relationship.
Degree
____ is used to depict the connectivity of entities; ____ is the actual number of connected occurrences for each entity.
Cardinality
Three Basic Types of Connectivity Relations:
- one-to-one relationship
- **one-to-many **relationship
- many-to-many relationship*
The Foreign Key (FK) and only the FK of the related table is the PK of another.
Weak or Non-identifying
The FK of the related table is also involved in its PK, along with being the PK of another table
Strong or Identifying
To determine relationship ____ , you have to look at it both ways and determine its categorization for each direction.
Participation
Participation Types:
When the ‘parent’ does not require a ‘child’ to be present.
Optional
Participation Types:
There is an entity required on each end for the relationship to make sense
Mandatory
____ is an entity that depends on another entity.
Weak entity
____ represents the main characteristic of an Entity.
Key attribute
An attribute can also have its own attributes. These attributes are known as ____.
Composite attribute
____ is a bottom-up approach in which two lower level entities combine to form a higher level entity.
Generalization
_ is opposite to Generalization. It is a top-down approach in which one higher level entity can be broken down into two lower level entities.
Specialization
When an Entity is related to itself it is known as ____.
Recursive Relationship
