Normalisation Demonstration

Summary

This podcast covers the essential process of database normalization, specifically focusing on achieving third normal form (3NF). The host explains how normalization reduces data duplication, ensures data consistency, and enhances table flexibility for complex queries. The episode walks through each step of normalization, starting from unnormalized data to first normal form (1NF), second normal form (2NF), and finally third normal form. Key concepts such as splitting attributes, identifying primary keys, and ensuring that non-key attributes depend solely on the primary key are discussed in detail.

Takeaways

• 📚 Normalization is the process used to design relational databases to eliminate unnecessary data duplication and ensure consistency.
• 📝 A well-normalized database allows for flexible data entry and enables complex queries across different tables.
• 🛠️ The goal of normalization is to achieve third normal form (3NF), ensuring tables are efficiently organized.
• 👀 In unnormalized data, attributes such as module number, level, module name, duration, and completion date are repeated, leading to inefficiency.
• 🔑 First normal form (1NF) is achieved by splitting the data into tables, identifying repeating and non-repeating attributes, and assigning a primary key to each table.
• 🗝️ In cases where the primary key is not unique, a composite key is created by combining attributes from different tables, ensuring uniqueness.
• ⚖️ Second normal form (2NF) is concerned with ensuring that every non-key attribute is fully dependent on the whole composite key.
• 🔄 If attributes are only partially dependent on the composite key, the table is further split into separate tables to achieve 2NF.
• ✅ To reach third normal form (3NF), all non-key attributes must depend solely on the primary key, which often requires splitting tables further.
• 🔗 Relationships between tables are maintained through the use of foreign keys, ensuring data integrity across the database.

Q & A

What is database normalization?

Database normalization is the process used to design a relational database efficiently, ensuring that tables are organized to prevent data duplication and maintain data consistency.

Why is normalization important in database design?

Normalization is important because it eliminates unnecessary data duplication, ensures data consistency across the database, and creates a flexible table structure that supports complex queries.

What is the goal of third normal form in database normalization?

The goal of third normal form is to ensure that all non-key attributes in a table depend solely on the primary key, eliminating any dependencies on other non-key attributes.

What are the signs of unnormalized data in a database?

Unnormalized data is characterized by duplicated values across rows, such as repeated module numbers, levels, module names, durations, completion dates, and results.

What is the first step to achieving first normal form (1NF)?

The first step to achieving first normal form is to split data so that attributes that repeat are separated from those that do not. In this case, trainee details like first name, last name, trainee number, and date of birth do not repeat, while module details do.

How is a unique identifier or primary key selected in the first normal form?

In the first table, the trainee number is selected as the primary key since it uniquely identifies each trainee. For the second table, the module number alone is insufficient as a primary key, so the trainee number is added to create a composite key.

What is second normal form (2NF) and how is it achieved?

Second normal form is achieved when each non-key attribute is fully functionally dependent on the entire primary key. In this case, the attributes dependent only on the module number (like module name and duration) are separated from those dependent on both module number and trainee number (like completion date and result).

How do you split tables when converting to second normal form?

To convert to second normal form, you split the table into two: one where attributes depend only on the module number and another where attributes depend on both the module number and trainee number.

What is the key criterion for third normal form (3NF)?

The key criterion for third normal form is that all non-key attributes must depend solely on the primary key, not on any other non-key attributes.

How do you ensure a table is in third normal form?

To ensure a table is in third normal form, you check that each non-key attribute depends only on the primary key. If an attribute depends on another non-key attribute, it is moved to a new table.