1.3.2 Flashcards
Database
A persistent , organised store of related data
Flat file Database
A single table that can be set up in a spreadsheet
Only suitable for very simple data handling requirements
Relational Database
Data is stored in seperate tables each of which represent a single entity. Tables are linked via common attributes to form relationships
Primary Key
The unique identifier
Secondary Key
Used to enable a database to be searched quickly
Foreign Key
The attribute which links two tables together
Entity Relationship Modelling
One-to-one :
Husband —— Wife
One-to-many :
Doctor —-<Patients
Many-to-Many :
Customers >—-Products
Normalisation
The process of coming up with the best possible design for a relational database
First Normal Form
-No attribute can contain more than one single value
Second Normal Form
-Is in 1NF
-No partial dependencies
Third Normal Form
-Is in 2NF
-Contains no non-key dependencies
Indexing
Method used to store the position of each record when ordered by a certain attribute
Used to look up and access data quickly
Capturing Data
Before data is added to a database , it must be captured or input
Selecting and Managing Data
Selecting only relevant data
Data can be managed using SQL
Exchanging Data
The process of transferring the data that has been collected
Referential Integrity
The process of ensuring consistency within a database
Transaction Processing
A single operation executed on data and must be processed in line with ACID
Atomicity
A transaction must be processed either entirely or not at all
Consistency
A transaction must keep the referential integrity rules between linked tables
Isolation
Simultaneous execution of transactions must lead to the same result
Durability
Once a transaction has been executed it will remain so even if for example , power is switched off
Record Locking
The process of preventing simultaneous access of records in a database in order to prevent inconsistencies
Redundancy
The process of having one or more copies of the data in physically different locations
