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813601
Relational Databases
Descripción
A Mind Map containing a compacted verion of everything you need to know for relationa database.
Sin etiquetas
as ict
databases
terminology
definitions
as ict
gcse + a level
Mapa Mental por
BadSideSecret
, actualizado hace más de 1 año
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Menos
Creado por
BadSideSecret
hace más de 10 años
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Resumen del Recurso
Relational Databases
File
Table
Record
All data about one person or thing.
Quite a few fields can be used to make a record e.g. name, address,age,date of birth.
Field
Primary Key
A field in a table which is unique and this helps to identify records or people
Referential integrity
Every foreign key value has a matching value in the appropriate primary key field.
A piece of data related to a person or thing
Foreign keys
A primary key in one table inserted as a normal field in another table
Attributes- Name,Age,Address
Records are stored in here.
Made of quite a few pieces of information, e.g. First Name, Address, Age
Entities- objects,people,things
RelationShips:
One to Many
Where one entity can have many relations- such as 1 doctor has many patient or 1 student has many exams
Many to many
where many entities can have many relationships e.g. 1 video can be hired by several customer BUT those customers can hire several videos
One to One
When one entity can only be related to one entite e.g. 1 man has 1 wife.
Many tables are stored in a file, this is the database.
Vast amounts of info can be stored!
Queries can be run to search for specific records.
Searching is what a query does.
Parameters are just search criteria
4 Types
Static-the parameters stay the same for ever.
Dynamic- you can change the search result sto what you need
Simple- only 1 parameter is used at a time
Complex-more than one parameter is used
Reports can be created from data stored or queries run
presents data taken from a query or from tables in a preformatted attractive manner
Validation can be used to reduce errors.
Validation!
Makes sure that the data is: accurate sensible,within acceptable boundaries.
Range Check- makes sure that the value entered is between 2 preset boundaries
Lookup Check-Allows only a limited amount of item to be selected
Length Check- checks that the data entered is a certain length.
Presence check- makes sure something is enteredin the field
NEVER MAKES SURE THAT THE DATA IS CORRECT!!!
Verification
Making sure that the data on the source document is the same as the object doucument.
Proof Reading- double checking your work basically.
Double entry- where two people input the same document and these are then compared any differences are then noted and rectified.
Forms Used to enter data.
A window/Screen with multiple spaces to enter data.
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