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AS 1.3.2 - Databases


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entity
a category of object, person, event or thing of interest to an organisation about which data is to be recorded
attribute
a specific type of data representing a particular characteristic of each data record; also known as a field or column
flat file database
a database with a single table (usually only concerning one entity)
relational database
a database consisting of a collection of tables in which entity relationships between records in different tables are created through common attributes, which can avoid duplicate storage of data
Entity1 (Attribute1, Attribute2)
format used for entity descriptions, with an entity called Entity1 and with attributes Attribute1 and Attribute2
primary key
an attribute that uniquely identifies each record in a table; this is automatically indexed and cannot be blank
composite primary key
when two or more attributes are used to uniquely identify records in a table
underlined
In an entity description, the primary key is ...
secondary key
a field, other than the primary key, which is indexed, so that the database can be searched quickly; the indexes are stored and maintained by the database software
one-to-one
relationship between two entities, such as Husband and Wife, or Country and Prime Minister
one-to-many
relationship between two entities, such as Mother and Child, or Customer and Order
many-to-many
relationship between two entities, such as Student and Course, or Film and Actor
entity relationship diagram
a diagrammatic way of representing the relationships between the entities in a database
foreign key
a primary key of one table which appears as an attribute in another table, which in turn creates a relationship between the two entities
italicised
In an entity description, the foreign key is ...
knowledge
Advantage of Flat File: simple to design and requires very little design ...
one place
Advantage of Flat File: all records are stored in ...
updated
Disadvantage of Flat File: there can be duplicate data, meaning each instance must be ...
complex queries
Disadvantage of Flat File: cannot carry out ...
different tables
Advantage of Relational Database: better security as different access rights can be set for ...
indexed
Advantage of Relational Database: fields can be ...
relational model
Disadvantage of Relational Database: the designer needs to understand the ...
referential integrity
consistency of table relationships, so that every foreign key refers to a valid primary key
normalisation
process used to come up with the best possible design for a relational database
entered as needed
tables in a relational database should be organised so that as many or as few records can be ...
capturing data
methods used to collect and input data into a database
manual
Method of Capturing Data: entering the data by hand / typing
web form
Method of Capturing Data: when a user fills out a form online and the submitted information is stored in a database
scanner
Method of Capturing Data: automatic entry, such as of information stored in barcodes
sensor
Method of Capturing Data: device that detects changes in environment and readings are automatically stored in the database
import
Method of Capturing Data: opening the data from another file into the database, such as from a CSV file
optical mark recognition
Method of Capturing Data: OMR, enters information based off marks, such as multiple choice questionnaires / exams
optical character recognition
Method of Capturing Data: OCR, enters data by using hardware and software to identify printed characters
selecting data
methods used to find record instances / data in a database
speed limit
Method of Selecting Data: could be selected before it is entered into the database, such as a speed camera only photographing vehicles exceeding the ...
structured query language
Method of Selecting Data: SQL, text based selection
query by example
Method of Selecting Data: QBE, graphical query language
managing data
methods used to maintain the data stored in a database
data integrity
the overall accuracy, completeness and consistency of data
values
Method of Managing Data: not allowing null ...
rules
Method of Managing Data: using data validation ...
cascade update
Method of Managing Data: maintaining referential integrity by using cascade delete and ...
archiving
Method of Managing Data: backing up the data and ...
access rights
Method of Managing Data: setting up ...
exchanging data
methods to transfer data between one computer system and another
electronic data interchange
Method of Exchanging Data: EDI, transferring data (often over the internet) without needing human intervention
CSV files
Method of Exchanging Data: exporting and importing files, such as ...
paper
Method of Exchanging Data: data is printed and then retyped or scanned in