What Are Relational Databases and Why Do We Still Use Them?

Relational databases have been the backbone of data management for decades. But in a world filled with NoSQL alternatives, why are they still so widely used? In this article, we’ll break down what relational databases are, how they work, and why they remain essential for many applications.

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What Is a Relational Database?

A relational database organizes data into structured tables with rows and columns. Each table represents an entity (e.g., customers, orders), and relationships between these entities are defined using keys.

Key Features of Relational Databases:

1. Structured Data: Data is stored in predefined schemas (tables).
2. Relationships: Tables can be linked via primary and foreign keys.
3. ACID Compliance: Ensures reliable transactions (Atomicity, Consistency, Isolation, Durability).
4. Query Language: Uses SQL (Structured Query Language) to interact with data.

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Why Are Relational Databases Still Relevant?

• Data Integrity:
  Ensures accuracy and consistency of data through constraints like primary keys and foreign keys.

• Complex Queries:
  SQL enables complex queries, joins, and aggregations that are harder to achieve in NoSQL.

• Broad Support and Maturity:
  Decades of optimization and a wide range of tools (e.g., MySQL, PostgreSQL, SQL Server).

• Transactional Applications:
  Ideal for systems requiring atomic transactions, such as banking, e-commerce, or inventory management.

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Example: E-Commerce Database Design

Let’s look at an example of a simple relational database for an e-commerce platform:

Table: Customers

CustomerID	Name	Email	Phone
1	Alice Doe	alice@example.com	123-456-789
2	Bob Smith	bob@example.com	987-654-321

Table: Orders

OrderID	CustomerID	OrderDate	TotalAmount
101	1	2025-01-14	120.50
102	2	2025-01-15	75.00

Relationship:

• The CustomerID in the Orders table is a foreign key referencing the CustomerID in the Customers table.

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Basic SQL Queries

1. Retrieve All Orders with Customer Names:

SELECT Orders.OrderID, Customers.Name, Orders.OrderDate, Orders.TotalAmount
FROM Orders
JOIN Customers ON Orders.CustomerID = Customers.CustomerID;

Result:

OrderID	Name	OrderDate	TotalAmount
101	Alice Doe	2025-01-14	120.50
102	Bob Smith	2025-01-15	75.00

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2. Add a New Order for a Customer:

INSERT INTO Orders (OrderID, CustomerID, OrderDate, TotalAmount)
VALUES (103, 1, '2025-01-16', 200.00);

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Real-Life Applications of Relational Databases

1. Banking Systems:
   Track customer accounts, transactions, and balances while ensuring data integrity.

2. E-Commerce Platforms:
   Manage products, customer orders, and inventory with structured relationships.

3. Hospital Management Systems:
   Store patient information, appointments, and billing data.

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Summary

Relational databases are structured, reliable, and powerful, making them indispensable for applications where data integrity and complex querying are crucial. While NoSQL databases are gaining traction, the reliability and maturity of relational databases ensure their continued relevance in industries like banking, e-commerce, and healthcare.