What is Data Normalization : Overview, Benefits and Understanding 1nf, 2nf, 3nf, and Bcnf

From small-scale startups to large-scale enterprises, it’s no secret that data has become a top priority for every business out there. As companies collect, store and analyze data, they build and utilize databases to handle them. In this growing field of big data, you may have come across a term called data normalization. Data normalization is very important to business operations and understanding it wholly can give any company a real advantage to grow further with Big Data.

What is Data Normalization?

Data normalization is the process of reorganizing data within a database so that users can utilize it for further queries and analysis. Simply put, it is the process of developing clean data. This includes eliminating redundant and unstructured data and making the data appear similar across all records and fields.

Keys in SQL

Before moving on to the different forms of data normalization, you need to first understand the concept of keys in SQL. A key can be a single column or a combination of columns that uniquely identify the rows (or tuples) in the table. It also helps to identify duplicate information and establish relationships between different tables.

Here are the most common type of keys:

  • Primary key - A single column used to uniquely identify a table
  • Composite key - A set of columns used to uniquely identify the rows in a table
  • Foreign key - A key that references the primary key of another table

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Data Normalization Forms

Data normalization can be divided into different types of normal forms. The most popular ones are 1NF, 2NF, 3NF, and BCNF. Let us dive into all these normal forms with the help of an example. Assume that a company has a database of all their employees and their key skills as shown in the table below. 

Salutation

Full Name

Address

Skills

Mr.

John Denver

12, Bates Brothers Road

Content writing, Social media marketing

Ms.

Mary Ann

34,  Shadowman Drive

Deep Learning, Data science

Ms.

Nancy Drew

4, First Plot Street

DBMS

1NF - First Normal Form

The most basic form of data normalization is 1NF which ensures there are no two same entries in a group. For a table to be in the first normal form, it should satisfy the following rules:

  • Each cell should contain a single value
  • Each record should be unique

The table in 1NF will look like this:

Salutation

Full Name

Address

Skills

Mr.

John Denver

12, Bates Brothers Road

Content writing

Mr.

John Denver

12, Bates Brothers Road

Social media marketing

Ms.

Mary Ann

34,  Shadowman Drive

Machine Learning

Ms.

Mary Ann

34,  Shadowman Drive

Data science

Ms.

Nancy Drew

4, First Plot Street

DBMS

2NF - Second Normal Form

In a 2NF table, all the subsets of data that can be placed in multiple rows are placed in separate tables. For a table to be in the second normal form, it should satisfy the following rules:

  • It should be in 1F
  • The primary key should not be functionally dependant on any subset of candidate key 

Let’s divide the 1NF table into two tables - Table 1 and Table 2. Table 1 contains all the employee information. Table 2 contains information on their key skills.

Table 1

Employee ID

Salutation

Full Name

Address

1

Mr.

John Denver

12, Bates Brothers Road

2

Ms.

Mary Ann

34,  Shadowman Drive

3

Ms.

Nancy Drew

4, First Plot Street

Table 2

Employee ID

Key skills

1

Content marketing

1

Social media marketing

2

Machine learning

2

Data science

3

DBMS

We have introduced a new column called Employee ID which is the primary key for Table 1. The records can be uniquely identified using this primary key.

In Table 2, Employee ID is the foreign key.

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3NF - Third Normal Form

For a table to be in the third normal form, it should satisfy the following rules:

  • It should be in 2F
  • It should not have any transitive functional dependencies 

A transitive functional dependency is when a change in a column (which is not a primary key) may cause any of the other columns to change.

In our example, if there is a name change (male to female), there may be a change in the salutation (Mr., Ms., Mrs., etc.). Hence we will introduce a new table that stores the salutations

Table 1

Employee ID

Full Name

Address

Salutation

1

John Denver

12, Bates Brothers Road

1

2

Mary Ann

34,  Shadowman Drive

2

3

Nancy Drew

4, First Plot Street

2

Table 2

Employee ID

Key skills

1

Content marketing

1

Social media marketing

2

Machine learning

2

Data science

3

DBMS

Table 3

Salutation ID

Salutation

1

Mr.

2

Ms.

3

Mrs.

Now, there are no transitive functional dependencies and our table is now in 3F. Salutation ID is the primary key in Table 3. Salutation ID in Table 1 is foreign to the primary key in Table 3.

BCNF - Boyce and Codd Normal Form

Boyce and Codd Normal Form is a higher version of 3NF and is also known as 3.5NF. A BCNF is a 3NF table that does not have multiple overlapping candidate keys. For a table to be in BCNF, it should satisfy the following rules:

  • It should be in 3F
  • For each functional dependency ( X → Y ), X should be a super key

Benefits of Data Normalization

As data becomes more and more valuable to any type of business, data normalization is more than just reorganizing the data in a database. Here are some of its major benefits:

  • Reduces redundant data
  • Provides data consistency within the database
  • More flexible database design
  • Higher database security
  • Better and quicker execution 
  • Greater overall database organization

A company can collect all the data it wants from any source. However, without data normalization, most of it will simply go unused and not benefit the organization in any meaningful way.

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Here’s What You Can Do Next

Data normalization is of top priority as organizations continue to use data on a scale like never before. Now that you have a basic understanding of data normalization, it is time to take a deep dive into the depths of this topic. As databases get more complex, there are higher-level normal forms that you need to learn. Simplilearn’s Big Data Engineer Certification Course features masterclasses by IBM experts to help you learn job critical skills via interactive live sessions, practical labs, and industry projects. Get started with this course today to get a leg up in your career.

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