Normalisation - OCR Computer Science A Level

Question	Answer
What 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
What 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
What 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
What 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)
Why 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

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	Created by Malachy Moran-Tun almost 2 years ago

	Copied by Malachy Moran-Tun almost 2 years ago