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1832365
GCSE Computer Science: Database
Descripción
Mapa Mental sobre GCSE Computer Science: Database, creado por MegzRevision el 04/01/2015.
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Resumen del Recurso
GCSE Computer Science: Database
Entity
An entity is a person or physical thing about which data is held in a database
Field
An individual box in the data table
Table = The whole thing
Record
An entire row of data
Database management system / DBMS
Allows you to create a table
Componants
Tables
Forms
Queries
Reports
Modules
Program within an application that performs a specific task which cannot be done by simply making a query or report
Datatypes
Text
Integers
Numbers with a decimal
Dates
Currency
Yes/No fields
Primary Key
One field is designated as the p.k
Each record must have a different value in the p.k
Uniquely identifies the record
Validating Fields
Minimise errors when data is entered into the database
Specifying a rule that the data must obey
Range check
Type check
e.g. number
Presence check
Data entered in the field
Format check
List check
Must be item on predefined list
Data Redundancy
Holding more data than necessary
Takes time and space
Can result in inconsistent data
Each entity has an attribute
Attribute = Field in the table which describes the entity
One-to-one
e.g. husband/wife
One-to-many
e.g. mother/children
Many-to-many
e.g. pupils/subjects
Separation of Data
Data held about various entities are held separatly from the applications that use it.
e.g. many departments in a school can look at or use the data
Reduces data redundancy
Data is consistent
Saves storage
Database
Persistent, organised store of data
Persistent = Data stored on a non-volatile storage device
Organised = Structured into tables
Allows separation of data between applications and the database
Allows multiple applications to use a single database
Can allow many users to simultaneously access the data and it's applications
Provides security in terms of access rights
Can provide automatic backups
Reports
Useful feature of a DBMS
Reports are produed based on queries
When a user asks for a report based on a query, the query will automatically be run first using the latest data, so the report is up-to-date
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