Karteikarten
Normalisation - OCR Computer Science A Level
Karten in diesem Stapel (5)
- 1What is Normalisation?> Process to ensure the best possible design for a relational database
> Ensures that
- No data is unnecessarily duplicated
- Data is consistent throughout the database (e.g., not conflicting entries in different tables)
- The structure of each table is flexible and allows entering as many or as few items as requied
- The structure allows for complex queries - 2What is First Normal Form?> All field (attribute) names must be unique
> Values in fields (attributes) should be from the same domain
> Values in fields (attributes) should be atomic, i.e., they are either updated in their entirety or not at all
> No two records may be identical
> Every table must have a primary key - 3What is Second Normal Form?> All the requirements of 1NF
plus:
> Remove any partial dependencies (i.e., none of the attributes depend on composite keys / only part of the primary key)
> Fix and Many-to-Many relationships as a result of removing partial dependencies - 4What is Third Normal Form?> All the requirements of 2NF (and 1NF)
plus:
> Remove any transistive dependencies (i.e., ensure that non-key fields are not dependent on eachother) - 5Why is Normalisation Important?> Data integrity (i.e., no data redundancy) is maintained, meaning there is no conflicting or unnecessary duplication of data
> Faster searching, due to smaller tables with fewer fields (also saving storage space)
> Records cannot be accidentally deleted in one-to-many relationships
Informationen
- Beschreibung
- A level Computer Science (Databases and SQL) Karteikarten am Normalisation - OCR Computer Science A Level, erstellt von Malachy Moran-Tun am 18/05/2022.
- Erstellt von
- Malachy Moran-Tun
- Aufrufe
- 10
- Verlauf
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- Erstellt von Malachy Moran-Tun · 18 Mai 2022
- Kopiert von Malachy Moran-Tun · 18 Mai 2022
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