1st, 2nd & 3rd Normal Form

• What is Normalisation? 

  • Normalisation is the process of organising a database to reduce data duplication and improve data accuracy and consistency 
  • Achieved by applying a set of guidelines (forms), each with specific rules and requirements 
  • Enhances database efficiency and maintainability 
  • Provides consistency within the database 
• FNF

  For a table to be in first normal form it must: 

  • Contain atomic values 
  • Each column in a table must contain single, indivisible values 
  • Have no repeating groups 
  • Columns must not contain arrays or lists of values 

  Have unique column names 

  Each column must have a unique name within the table 

  Have a unique identifier (primary key) 

  Each row must have a unique identifier to distinguish it from other rows 
• Second Normal Form (2NF) 

  For a table to be in second normal form it must: 

  • Fulfil all 1NF requirements 
  • Only apply to tables with a compound primary key 
  • Have full functional dependency 
  • All non-prime attributes (attributes not part of the primary key) must be fully dependent on the primary key 
  • Have no partial dependencies 
  • Non-prime attributes must not depend on only part of the primary key (in case of a composite primary key) 
  • Separate tables should be created for partially dependent attributes 
• Third Normal Form (3NF) 

  For a table to be in third normal form it must: 

  • Fulfil all 2NF requirements 
  • Have no transitive dependencies 
  • Non-prime attributes must not depend on other non-prime attributes 
  • Have each non-prime attribute dependent solely on the primary key, not on other non-prime attributes 
  • Have separate tables for attributes with transitive dependencies, and the tables should be linked using a foreign key