Database Normalization: First and Second Normal Forms

Questions and Answers

Cosa implica una dipendenza completa tra le colonne di una tabella?

Tutte le colonne dipendono dallo stesso valore chiave primaria

Quale forma normale è essenziale per garantire una completa dipendenza tra le colonne di una tabella?

Seconda Forma Normale (2NF)

Cosa si intende per dipendenza funzionale tra due insiemi di dati?

Ogni elemento in un insieme determina esattamente un elemento nell'altro insieme

Qual è l'obiettivo principale della transizione alla Seconda Forma Normale?

Migliorare le prestazioni complessive del database Signup and view all the answers

In che modo la transizione alle forme normali superiori rende più efficiente la struttura del database?

Migliorando la pulizia e l'efficienza della struttura Signup and view all the answers

Cosa richiede la Prima Forma Normale (1NF) per ogni tabella?

Valori atomici senza gruppi ripetuti Signup and view all the answers

Cosa significa atomicità in una tabella di database?

Riferimento a valori semplici che non possono essere suddivisi Signup and view all the answers

Qual è uno degli obiettivi principali della chiave univoca in una tabella di database?

Prevenire record duplicati Signup and view all the answers

Cosa fa la Seconda Forma Normale (2NF) per migliorare la struttura della tabella rispetto alla Prima Forma Normale (1NF)?

Elimina dipendenze parziali dalle tabelle Signup and view all the answers

Cosa significa che un attributo in una tabella di database è considerato atomico?

Il valore non può essere suddiviso senza perdere significato Signup and view all the answers

Study Notes

Database Normalization

Database normalization is a process of organizing data into logical arrangements called schemas. These logical structures help prevent data redundancy while ensuring data integrity. There are three levels of database normalization: First Normal Form (1NF), Second Normal Form (2NF), and Third Normal Form (3NF). In this article, we will focus on the first two forms.

First Normal Form (1NF)

First Normal Form requires that each table contains only atomic values, which means there are no repeating groups. However, some sources suggest that it also includes constraints such as unique keys and referential integrity.

Atomic Values

In a table, atomicity refers to how simple attributes are compared with complex ones. An attribute is considered atomic if its value cannot be broken down into smaller parts without losing meaning. For example, a simple color code like 'Red' is atomic, whereas a more complex term like 'Blue-green' would not be atomic since it can be broken down further into 'Blue' and 'Green'.

Unique Keys

A unique key ensures that every record in a table has a unique identifier. This helps prevent duplicate records within the same table. Unique keys also ensure that the key holds one value per row, meaning that it must be unique for each row.

Second Normal Form (2NF)

The Second Normal Form goes beyond the First Normal Form by eliminating partial dependencies from tables. Partial dependency occurs when some columns depend on other columns, creating unnecessary redundancies in the database.

Complete Dependencies

Complete dependency exists when all columns in a table correspond to all rows. It implies that all columns in the table have a functional dependency on the primary key and that they always exist together in the same table. A complete dependency is essential for ensuring the Second Normal Form.

Functional Dependency

Functional dependency is a relationship between two sets whereby every element in one set determines exactly one element in another set. If a relation satisfies both conditions of being a key and having a total supply determined by the sums of the quantities, it is said to satisfy the functional dependency.

By transitioning to Second Normal Form, databases can reduce redundancy and improve overall performance. As you progress through higher normal forms, the structure becomes increasingly efficient and streamlined.