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Unit 18: Relational Database Development - Coggle Diagram
Unit 18: Relational Database Development
P1: Explain the principles of relational database models and how they are used to provide reliable data structures.
P2: Explain the process of normalisation within a relational database.
Normalisation
The process of Normalisation (Normal Forms)
NF2
removes functional dependencies
Functional dependencies are groups of columns that depend on each other rather than on the key of the table.
NF3
removes more subtle dependencies called Transient dependencies
Transient dependencies are where a field depends more on another column for its meaning than on the Table key.
NF1
involves getting rid of all
repeating groups and arrays.
UNF (un-normalised form)
Inefficient
BCNF (Boyce-Codd normal form)
What is normalisation
Why is it needed
reducing Data
redundancy
less storage required
Faster file reading
anomalies
Insertion anomalies
you can’t enter a record in
because some data is missing.
Update anomalies
when the same data is stored
in more than one place.
whenever you have to make a change to
the data, you must do it in several places.
higher chance of misinputting data
Deletion anomalies
occur when deleting a record
accidently causes other data to be lost.
M1: Analyse the principles of relational database models, the importance of normalisation and how they can provide reliable and efficient data structures.
D1: Evaluate the principles of relational database models, the importance of normalisation and how they can provide reliable and efficient data structures.