Normalized tables are:

  • Easier to understand
  • Easier to ehnahce and extend
  • Protected from anomalies (insertion, update, delete)

First Normal Form (1NF):

  • Using row order to convey information is not permitted
  • Mising data types within the same column is not permitted.
  • Having a table without a primary key is not permitted
  • Repeating groups are not permitted

Second Normal Form:

  • (Informally) Each non-key attribute must depend on the entire primary key.
  • So in order to have 2NF, we remove “Partial Dependency”.

Third Normal Form:

  • This form forbids the dependency of a non-key attribute to another non-key attribute.
  • Every (non-key) attribute in a table should depend on the key, the whole key, and nothing but the key.
  • In order to have 3NF, we remove “Transitive Dependency”.
  • Boyce-Codd Normal Form: Every attribute in a table should depend on the key, the whole key, and nothing but the key.

Fourth Form:

  • In order to have 3NF, we remove “Multi-Valued Dependency”
  • Multi-Valuded Dependency
    • A-»B is Multi-Valuded Dependency for a single value in A, more than one value of B exists in table.

References:

Last Updated: Sunday, 16 March, 2025 14:25 AEDT
Author: Madhav Om