Measure of the accuracy and the integrity of data between applications and across an enterprise
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Data Redundancy
Means that the same data is present in more than one table. Or in a flat file database, the records are partly duplicated
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Data Independance
Form of database management that keeps data separates from all programs that make use of it. It is a type of data transparency that matters for a centralized DBMS.
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Relational Database
A relational database has more than one table and the tables are linked using key fields
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Primary Key
Provides a way to uniquelt identify every record in a table
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Foreign Key
Used to link together and create a relationship. It is a field in one table that is linked to the primary key in another table.
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Data Integrity
Ability to force records to be consistent
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Entity
Each table is about an object, person or thing. These are known as Entities
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Attributes
An entity is made up of a number of attributes. It describes the facts, details or characteristics of an entity.
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Database Relationships
Links between Entities
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Entity Relationship Diagram
Can be shown in the form of a diagram. Take form in a one to one, one to many or many to many relationship
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Designing Relationships
The 'Many' side is usually the foreign key. The 'One side' is usualyl the primark key.
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Database Normalisation
A Technique used for designing relational database tables to minimize duplication of information and in doing so, to safeguard the database against logical or structural programs
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What are the rules for Database Normalisation?
1. Organise the Data Efficiently. 2. Eliminate redundant data. 3.Ensre only related data is stored
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What are Normal Forms?
Good rules that have been developed that allow a database to be designed with different levels of efficiency. The designer can choose what form he needs depending on what kind of database he is going to develop.
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What is a First Normal Form?
To be in 1st Normal Form it must meet a set of rules which are: 1. There are no column with repeated or similar data - 2. Each data item cannot be broken down any further and must be atomic - 3. Each Row is unique - 4.Each field has a unique name
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What is a 2nd Normal Form?
The other rules for 2nd normal form are - 1. Non-key Attributes must depend on every part of the primary key and 2. The table MUST be in 1st Normal Form
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What is a 3rd Normal Form
For the 3rd Normal form there are more rules. 1. It is already in 2NF and 2. There are no non-key attributes that depend on another non-key attribute
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Other cards in this set
Card 2
Front
Data Redundancy
Back
Means that the same data is present in more than one table. Or in a flat file database, the records are partly duplicated
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