Database System Concepts, Database Schema, Relational Model Flashcards
A shared collection of logically related
data, and a description of this data,
designed to meet the information needs
of an organization.
Database
A software system that enables users
to define, create, maintain, and control
access to the database.
Database Management System
allows users to specify the data types and
structures, and the constraints on the
data to be stored in the database
Data Definition Language
allows users to insert, update, delete and
retrieve data from the database
Data Manipulation Language
provides controlled access to the data
stored in the database.
Data Control Language
the overall description of a database.
Database schema
part of the database that is relevant to
each user. This is the users’ view of the
database.
external schema
describes what data are stored in the database, and what relationships exist among those data.
conceptual schema
describes how the data are stored in the database.
internal schema
A table consisting of one or more columns and zero or more rows.
Relation
A named column of a relation.
Attribute
set of allowable values for one or
more attributes
Domain
A row of a relation
Tuple
The number of attributes it contains.
Degree of a Relation
The number of tuples it contains.
Cardinality of a Relation
A column or group of columns whose values uniquely identify each row of the table
Primary Key
A column or group of columns that
is a primary key elsewhere.
Foreign Key
This rule states that a primary key column cannot contain a null value.
Entity Integrity Rule
This rule states that every foreign key value must refer to existing primary key values or be null
Referential Integrity Rule
A graphical representation of the
entities, and the relationships between
entities, within an information system.
Entity-Relationship Diagram
A person, animal, plant, place, thing,
substance or idea that can be uniquely
identified by type and occurrence. A
construct that represents what the
database keeps track of.
Entity
An association between two entities.
Relationship
A qualifier of an entity describing its character, quantity, or degree.
Attribute
