Flashcards
Week 4 - Normalisation
Cards in this deck (7)
- 1Data normalisation- Systematic series of steps for progressively refining the data model
- Formal approach to analysing relations based on their PK and functional dependencies
- Helps avoid data anomalies and redundancy - 2Types of dependencies- Full dependency - attribute is dependent on all attributes in the composite PK
- Partial dependency - attribute is dependent on only a subset of the PK
- Transitive dependency - attribute is dependent on another attribute that is not part of the PK
- Total dependency => attribute A determines B and attribute B determines A - 3Unnormalised form (UNF)- Raw representation mapped from inspection of the form
- Single named representation
- No PK has been identified - 4First normal form (1NF)- Identify PK (unique for each row)
- All attributes are functionally dependent on all or part of PK
- Valid relation => entity integrity, no repeating groups (multivalued attributes)
- Partial dependencies are noted in diagram - 5Second normal form (2NF)- All non-key attributes are fully functionally dependent on any CK (no partial dependencies)
- Transitive dependencies are noted in diagram - 6Third normal form (3NF)- No non-key attributes are dependent on another non-key attribute (no transitive dependencies)
- All dependencies are noted in diagram - 7Attribute synthesis- Join together relations, which have an identical PK
- Ensure attribute names are consistent
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- Computer Science (FIT2094: Databases) Flashcards on Week 4 - Normalisation, created by Melina Mackey on 01/11/2020.
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- Melina Mackey
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- Created by Melina Mackey · Oct 19, 2020
- Copied by Melina Mackey · Oct 25, 2020
- Copied by Melina Mackey · Nov 1, 2020
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