Topic 3: Database Concepts I Flashcards
Attributes
Characteristics of entities.
Cardinality
The specific number of allowed entity occurrences associated with a single occurrence of the related entity by assigning a specific value to connectivity.
Client–server System
A computing model that is based on distributing functions between two types of independent and autonomous processes: clients and servers.
Composite Key
A combination of more than one attribute to form one primary key. It indicates an M:N (many-to-many) relationship between the columns.
Conceptual Models
Models that focus on a logical view of what is represented in the database.
Controlled Redundancies
Redundancies that are allowed for the convenience of structuring data, data manipulation or reporting.
Data
Raw facts relating to or describing a single business transaction or event.
Data Anomalies
Inconsistencies or errors that exist in a database because of entry or changes.
Data Integrity
Consistent and correct representation regardless of where data are sourced from within a file system.
Data Redundancy
The situation where the same data are recorded and stored in multiple locations, which can lead to data inconsistency and anomalies.
Database
A shared computerised structure that captures, stores and relates data.
Database Administrator
A person who controls access by users to the database, maintains the data dictionary and oversees backup and recovery in the DBMS.
Database Management System (DBMS)
A group of programs that manipulate the database and provide the interface between the database and the user as well as other application programs.
Database Models
Diagrams of data entities and their relationships.
Database System
A system of hardware, software, people, procedures and data that allow the capture, storage, management and use of data within a database environment.
Deletion Anomalies
Data anomalies that occur when the deletion of data about an entity inadvertently deletes data about another entity.
Entities
Representations of real-world things or objects that are involved in a process and correspond to a table in a relational database.
Entity–relationship Model
A data model that graphically depicts relationships between entities and attributes.
External Models
Models that relate to the end-users’ views of data.
Field
A characteristic of a record that contains data that have a specific meaning.
File
A collection of records that are related.
Foreign Key
An attribute whose values must match the primary key in another table.
Hardware
Physical devices including the computer and network.
Implementation Models
Models that show how the data are represented in the database, including the structures implemented.
Information
Data or facts that are processed in a meaningful form.
Insertion Anomalies
Data anomalies that occur when new data are entered into the file and not all occurrences are updated.
Logical Representation
A model that represents data and their relationships independent of hardware and software. This representation can then be used to select a database management system (DBMS).
Many-to-many Relationship (M:N)
A relationship between two entities in which the cardinality of both entities in the relationship is many.
Modification Anomalies
Data anomalies that occur when a field value is changed and not all occurrences are updated.
Normalisation
A set of rules and a process of assigning attributes to entities to eliminate repeating groups and data redundancies, and to form tables representing entities that promote structural and data independence.
One-to-many Relationship (1:N)
A relationship between two entities in which the cardinality of one entity in the relationship is one and the other entity’s cardinality is many.
One-to-one Relationship (1:1)
A relationship between two entities in which the cardinality for each entity is one.
Operating System
Computer programs that control hardware to interface with software application programs.
Physical Representation
A model that presents all the database storage details including all specifications for hardware and software.
Primary Key
An attribute (or column) that uniquely identifies a particular object (or row).
Procedures
The instructions and rules that govern the design and use of the software outside programming.
Record
A connected set of fields that describes a person, place or thing.
Relational Database
A database that stores data in a number of tables.
Software
Computer programs that are written in programming languages or code that instruct the operations of a computer.
Structural Independence
A data attribute that exists when changes in the database structure do not affect access.
Structured Query Language (SQL)
A database query language that allows the user to specify what must be done without having to specify how it is to be done.
Table
A collection of columns (attributes) and rows (objects) that describe an entity.
