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Normalisation (Translating an ER diagram into relations (Create one table…
Normalisation
Translating an ER diagram into relations
Create one table for each entity
Create single column primary key for the one of the one to many, using an arbitrary unique identifier
For the many of the one to many use the primary key of the parent entity in the table as foreign keys
If a many of the one to many has a natural primary key, use that single column as the primary key
There are two approaches to normalisation
First is to work from an ER diagram
Second is to use the theoretical concepts
Normal Forms
The theoretical rules that the design of a relation must meet are known as normal forms
There are six nested normal forms
First normal form
In first normal form it meets the criteria of
The data is stored in a two dimensional table
There are no repeating groups
Second normal form
Second normal form relations are defined by
The relation is in first normal form
All non key attributes are functionally dependent on the entire primary key
Third normal form
Definition of third normal form
The relation is in second normal form
There are no transitive dependencies
Boyce Codd normal form
To be in this normal form it must be
The relation is in third normal form
All determinants are candidate keys
Fourth normal form
Fourth normal form must have
The relation is in BCNF
There are no multi-valued dependencies
Fifth normal form
Fifth normal form must be
The relation is in fourth normal form
All join dependencies are implied by the candidate keys