State 3 ways redundancies can be minimised
- Closely related attributes are found in the same relation (table).
- Each relation contains aminimumnumber of attributes
- Each attribute value is stored aminimumnumber of times (ideally only once)
What would insertion anomalies consist of?
two inconsistent records containing conflicting data with no indication of which one is correct.
What would deletion anomalies consist of?
lost data from the database, and records are no longer complete.
What would modification anomalies consist of?
If any related row is missed in the modification of data, we are again left with inconsistent data.
What is a functional dependancy?
Functional dependency is a relationship that exists when one attribute uniquely determines another attribute.
What is the definition of Normalisation?
The procedure for refining database structures.
What is the aim of Normalisation?
To eliminate redundancy.
What are the conditions that must be met for data to be in First Normal Form?
- All attributes must be atomic
- There must be no repeating groups of attributes
- There must be a primary key
- All non-key attributes must be functionally dependent on the primary key
What are the conditions that must be met for data to be in Second Normal Form?
There must be no partial dependencies
What are the conditions that must be met for data to be in Third Normal Form?
There must be no transitive dependencies
What is a Surrogate (Synthetic) key?
A serial number or code with no intrinsic meaning added to provide a single unique attribute to be the primary key
What can a Data Warehouse be used for?
Designed for high data volumes and quick reporting
