Information Systems And Databases Flashcards
Characteristics of Information systems
Organisation of data into Information
Analysis of Information to give knowledge
What are the types of information systems
Transaction processing systems
Decision Support Systems
Expert systems
Managment information systems
Office automation systems
What is a Database
A database is an organised collection of data.
What are the four main advantages that Computer-based Databases have over non-computer databases
Easily edited
Large storage
Fast Retrieval
Display options
what are the four data structures of a database
File
Record
Field
Character
what are the two types of databases
Flat file databases and Relational databases
What are the four different types of Keys
Single key
Composite key
Primary key
Secondary key
what is a key
Keys are fields that are used to sort and retrieve information
What is a single key
a single key is a field in which each item of data is unique
what is a composite key
a composite key or also known as a compound key is made by joining two or more fields together.
what is a primary key
a primary key is a single key or compound key that must have a value
what is a secondary key
a secondary key is a field that contains useful items of data often used in searches.
what is a file
a file is a block of data.
what is a record
a record is a collection of facts about one specific entry in a database.
what is a field
a field is a specific category of data in a database
what is a character
a character is the smallest unit of data that people can use
What is a relational database
a relational database organises data using a series of related tables.
What is a flat file database
a flat file database organises data into a single table and is suitable for many small applications.
What is a schema
A schema is the data definition for a database. it is an organised plan of the entire database that shows how and where the data is found, descriptions of the data, and the data’s logical relationships. In relational databases schemas define the entities, attributes and relationships
what are the three things that Schema’s define in a relational database
entities
attributes
relationships
what is an entity
an entity is a specific thing about which information is collected and stored. In a flat file database there would be a separate file for each entity
what is an attribute
an attribute is a defined property of an entity, examples would include LastName, FirstName and PhoneNumber.
What is a relationship
a relationship is the way the entities are related to each other, in relational databases each entity are related using keys.
what are the four types of relationships
one-one
one-to-many
many-to-one
many-to-many
what is a one-to-one relationship
a one-to-one relationship occurs when each record in the first entity is related to exactly one record in the second entity
what is one-to-many or many-to-one relationship
a one-to-many relationship occurs when one record in the first entity is related to many records in the entity, but any record in the second entity relates to only on record in the first entity. Vice versa for many-to-one relationships
what is a many-to-many relationship
a many-to-many relationship occurs when each record in the first entity is related to many records in the second entity, and each record in the second entity is related to many records in the first entity.
what is a foreign key
a foreign key is an attribute(field) of a table that is a primary key of another table.
what is a table in a database
a table is the organisation of data into columns and rows, it is sometimes reffered to as a relation.
what is a row in a table also known as
tuple of an entity or one record.
what is a form
a form is used to view, enter, and change data in a table
what is data modelling
data modelling is the process of identifying entities, the relationships between those entities and the attributes of those entities. They are used to develop a schema for the database.
what are the three main tools used for data modelling
data dictionaries
schematic diagrams
normalisation
what are data dictionaries
a data dictionary is a comprehensive description of each field (attribute) in the database.
what are the characteristics of each item in a database
field name
field size
data type
field description
what is a field name
a field name is the name of the field
what is a data type
a data type (or field type) is the kind of data that can be stored in the field
what is the field size
field size or width is the number of characters allowed in each field.
what is a description in a data dictionary
description specifies the contents of a field
what is meta data
it is information about data
what is data redudancy
data redudancy is the undersiable duplication of data within a database
what is a Schematic diagram
Schematic diagrams are graphical tools that help define the database and develop a schema. A common schematic diagram is an entity-relationship diagram.
What is an Entity-relationship diagram (ERD)
an Entity-relationship diagram is a graphical method of identifying the entities and showing the relationship between them. It helps determine the data to be included in and excluded from the databases.
what is normalisation
Normalisation is the process of organising data into tables so that the results of using the database are unambiguous and as intended. It is a refinement process that aims to reduce data redundancy. Normalisation results in a database that is more efficent but more complex because the data is separated into more tables.