ICT- Relational Database Concepts

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  • Created by: TOPHAMS
  • Created on: 25-02-17 14:35
What is an Atomic Value?
A value that cannot be Divided
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What is 1st Normal Form?
All repeated data fields are removed from the main table and placed in a table of their own. Primary Keys are allocated to tables. Atomic values
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What is 2nd Normal Form?
Removes Partial Key dependencies. Primary Keys are allocated to new tables
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What is 3rd Normal Form?
Primary Keys are allocated to new tables. Foreign Keys are allocated. Relationships link the tables together
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What is a Relational Database?
The data is stored in independent, self contained tables. Foreign keys link the data in tables together
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What are the benefits of a Relational Database?
Easy to add/change structure of the database. Referential integrity maintained
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What are the drawbacks of a Relational Database?
Needs complex software. Can be complicated to administer/set up
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What is a Database?
A large collection of data items and links between them
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What are Records?
The basic unit of data stored in a data file
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What are Fields?
Is part of a record designed to hold a single data item of a specified type
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What is a Primary Key?
It is a unique value which is used to identify a record
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What is a Foreign Key?
A foreign key is a field in a table that is not a key field in the table but is a key field in another
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What is a Parameter Query?
These are queries that search for data using a value as the search criteria – for example: County is UK – the UK is the parameter. A parameter can be static or dynamic.
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What is a Complex query?
These are parameter queries with more than one parameter Use of: AND, OR, NOT For example: Name is SMITH and lives in ASHFORD
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What is a Data Dictionary?
A database about a database containing Metadata
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What are the advantages of Normalisation?
No redundant data - Easier to maintain
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What are the Disadvantages of Normalisation?
Cannot store past data - Reduced database performance
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What is a Composite Key?
Where there is not a single field suitable as a primary key, two or more fields can be combined to make a primary key.
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Other cards in this set

Card 2

Front

What is 1st Normal Form?

Back

All repeated data fields are removed from the main table and placed in a table of their own. Primary Keys are allocated to tables. Atomic values

Card 3

Front

What is 2nd Normal Form?

Back

Preview of the front of card 3

Card 4

Front

What is 3rd Normal Form?

Back

Preview of the front of card 4

Card 5

Front

What is a Relational Database?

Back

Preview of the front of card 5
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