Database Normalization is a technique of organizing the data in the database. Database Normalization is a systematic approach of decomposing tables to eliminate data redundancy(repetition) and undesirable characteristics. For example, Insertion, Update and Deletion anomalies. It is a multi-step process that puts data into tabular form, removing duplicated data from the relation tables.
Normalization is used for mainly two purposes.
- Eliminating redundant(useless) data.
- Ensuring data dependencies make sense i.e. data is logically stored.
First Normal Form (1NF)
For a table to be in the First Normal Form, it should follow the following 4 rules:
- It should only have single(atomic) valued attributes/columns.
- Values stored in a column should be of the same domain
- All the columns in a table should have unique names.
- And the order in which data is stored does not matter.
Second Normal Form (2NF)
For a table to be in the Second Normal Form,
- It should be in the First Normal form.
- And, it should not have Partial Dependency.
Third Normal Form (3NF)
A table is said to be in the Third Normal Form when,
- It is in the Second Normal form.
- And, it doesn’t have Transitive Dependency.
Here is an example of a denormalized table
Film Agents Info
| AgentId | Agent Name | Agency Name | Office Location | Office Contact | Customer1 | Custo2 |
| A1 | A&I Gold | New Cine | Los Angels | 111222333 | BreadPtch | Brian |
Let’s Take This table to 1NF (First Normal Form).
We shall Split the above table into two tables.
Agent Info
| AgentId | Agent Name | Agency Name | Office Location | Office Contact |
Customer Info
| CId | AgentId | Customer Name | Customer City | CustomerPincode |
Let’s Take the above tables to 2NF (Second Normal Form) We Shall split the above two tables into four tables.
Agent info
| AgentId | AgentName | AgencyId |
Agency Info
| AgencyId | AgencyName | OfficeLocation | Office Location |
Customer Info
| CId | CustomerName | CustomerCity | CustomerPincode |
CustomerAgents
| AgentId | CustomerId |
Let’s Take the above tables to 3NF (Third Normal Form).
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We Shall split the above two tables into five tables.
Agent info
| AgentId | AgentName | AgencyId |
Agency Info
| AgencyId | AgencyName | OfficeLocation | Office Location |
Customer Info
| CId | CustomerName | CustomerPincode-FK |
CustomerPinCodes
| CustomerPinCodes | CustomerCity |
CustomerAgents
| AgentId | CustomerId |
