Definitions

Incoherence

________: impossible value of the requested information.

ER diagram

________: graphical representation of all entities and relationships with their attributes.

Discriminant

________: set of attributes which allow distinguishing between instances of the weak entity that depend on the same instance of strong entity (underline points)

Inconsistency

________: same query gives different results depending on its implementation.

Relationships

________: association b between different related entities instances.

Aggregation

________: grouping of relationships and participating entities into a new entity.

Generalization

________: process summarizing multiple entities into a high level entity based on common characteristics (reverse of specialization)

Data integrity

________: always guarantee the acid properties (atomicity, consistency, isolation, durability)

Cardinality

________: maximum number of instances of an entity that may be associated with an instance of the other entity involved in a relationship.

Functional requirements

________: description of the operations to be carried out with the data.

Foreign key

________: a set of table attributes that are primary key of another table and relates the two tables.

Database

________: way to store data ensuring persistent content and efficient access.

Partial participation

________: not all elements of A must be related to some element of B (single line)

Attributes

________: entities and relationships information or features → ellipses.

Total participation

________: all elements of A must be related to some element of B (double line)

Specialization

________: partition of an entity in specific groups.

Data heterogeneity

________: flexible logical structure that allows to keep the same type of information (varying on number and type)

Candidate keys

________: minimum set of attributes that uniquely identifies each instance and do not contain other keys or redundant attributes.

Cardinality 1 1

________: a customer can only have one loan.

Relationships

________: association of several entities → rhombus.

Database

way to store data ensuring persistent content and efficient access

Database system

computer storage systems for the manipulation of related data volumes in centralized system (multiuser)

Data homogeneity

logical structure which always keeps the same type of information (varying on number and type)

Data heterogeneity

flexible logical structure that allows to keep the same type of information (varying on number and type)

Data integrity

always guarantee the acid properties (atomicity, consistency, isolation, durability)

Incoherence

impossible value of the requested information

Inconsistency

same query gives different results depending on its implementation

External

presentation of the data to users

Conceptual

logical description of data

Internal

organization and storage on physical files

Back-end

software which executes all functions specified in a DBMS

Front-end

applications executed over a DBMS

Data requirements

description of data and the relationship between them

Functional requirements

description of the operations to be carried out with the data

ER diagram

graphical representation of all entities and relationships with their attributes

Entities

object (event) from real word → rectangles

Relationships

association of several entities → rhombus

Attributes

entities and relationships information or features → ellipses

Candidate keys

minimum set of attributes that uniquely identifies each instance and do not contain other keys or redundant attributes

Primary key

set of attributes that uniquely identify entities instances

Relationships

association b between different related entities instances

Cardinality

maximum number of instances of an entity that may be associated with an instance of the other entity involved in a relationship

Cardinality 1-1

a customer can only have one loan

Cardinality 1-N

a client can have more than one loan

Cardinality N-1

a loan can be shared among multiple clients

Cardinality N-N

no restrictions

Unary relationship

relation to the same entity

Binary relationship

relationship between two entities

N-ary

relationship between n known entities

Total participation

all elements of A must be related to some element of B (double line)

Partial participation

not all elements of A must be related to some element of B (single line)

Weak entities

entities that do not have enough attributes to define a primary key (double rectangle)

Discriminant

set of attributes which allow distinguishing between instances of the weak entity that depend on the same instance of strong entity (underline points)

Specialization

partition of an entity in specific groups

Generalization

process summarizing multiple entities into a high level entity based on common characteristics (reverse of specialization)

Aggregation

grouping of relationships and participating entities into a new entity

Foreign key

a set of table attributes that are primary key of another table and relates the two tables