1NF 2NF 3NF DBMS

Summary

This script emphasizes the importance of normalization in database design to reduce data redundancy and enhance security. It outlines the process of achieving different normal forms: First Normal Form by eliminating repeating values or groups, Second Normal Form by resolving partial dependencies in composite keys, and Third Normal Form by eliminating transitive dependencies. Each step is crucial for creating a flexible, secure, and efficient database structure.

Takeaways

• 📚 Normalization is crucial in database design to reduce data redundancy and improve data organization.
• 🔐 Database security is enhanced through normalization as it involves creating more tables which can restrict access to sensitive data.
• 📈 The process of normalization should follow a sequence: First Normal Form (1NF), Second Normal Form (2NF), and then Third Normal Form (3NF).
• 🚫 A table in 1NF must avoid repeating values within a group and repeating groups within the table.
• 🔑 To achieve 1NF, if a table has repeating values or columns, these should be separated into distinct tables and linked appropriately.
• 🔄 Composite keys, which consist of more than one column, can lead to partial dependencies and are a consideration for 2NF.
• 📝 For a table to be in 2NF, it must be in 1NF and have no partial dependencies where non-key columns depend only on part of the composite key.
• 🔄 In 3NF, tables must be in both 1NF and 2NF, and there should be no transitive dependencies where non-key columns depend on other non-key columns.
• 🔍 Identifying and removing transitive dependencies, such as guessing one non-key column from another, is essential for achieving 3NF.
• 💡 Examples provided in the script, such as employee phone numbers, student results, and match capacities, illustrate how to apply normalization rules in real-world scenarios.

Q & A

What is the primary purpose of normalization in database design?

The primary purpose of normalization in database design is to reduce data redundancy and improve data integrity by organizing data into well-structured tables.

Why is it important to follow the sequence of normalization forms when designing a database?

Following the sequence of normalization forms is important because each form builds upon the previous one. You cannot bypass earlier forms and directly go to a higher normal form, as each step ensures the database adheres to specific structural rules that prevent data anomalies.

What are the two criteria that a table must meet to be in the first normal form?

A table must meet two criteria to be in the first normal form: it should not have repeating values in a group, and it should not have repeating groups in the table.

How does the example of an employee table with multiple phone numbers violate the first normal form?

The example of an employee table with multiple phone numbers violates the first normal form by having repeating values in a column, as the phone numbers are listed in a single column, which goes against the rule of having no repeating groups.

What is a composite key and why is it necessary in a database?

A composite key is a primary key composed of more than one column, used when a single column is not sufficient to uniquely identify a record. It is necessary to ensure that each record in the database can be uniquely identified.

Can you explain partial dependency and how it relates to the second normal form?

Partial dependency occurs when a non-key column depends on only a part of a composite key rather than the entire key. To achieve the second normal form, the table must be free from partial dependencies, ensuring that non-key columns depend on the entire primary key.

What is a transitive dependency and how does it violate the third normal form?

A transitive dependency occurs when a non-key column is dependent on another non-key column or when a non-key column can be determined from other non-key columns. This violates the third normal form, which requires that non-key columns should only depend on the primary key.

How does normalization affect database security?

Normalization can enhance database security by creating more tables that can be used to restrict access to sensitive information. By segmenting data into multiple tables, it becomes easier to implement security measures that control access to specific data sets.

What is the solution to the problem of repeating columns in a table?

The solution to the problem of repeating columns is to remove the columns that are causing the issue and create separate tables for those columns, then link them back to the original table using a foreign key.

Why is it beneficial for a database to handle more tables rather than having tables with repeating values or columns?

Handling more tables is beneficial because it adheres to the principles of normalization, which reduces redundancy and improves data integrity. Databases can efficiently manage multiple tables, but they struggle with performance and consistency when dealing with repeating values or columns.