Introduction 

Every software application, whether a simple web app or a complex enterprise system, revolves around one essential concept — CRUD operations. CRUD stands for Create, Read, Update, and Delete — the basic building blocks that allow applications to interact with data.

Understanding CRUD is the first step in becoming a developer, as it forms the backbone of how applications manage data. Whether you're working on the frontend, backend, or full-stack development, mastering CRUD gives you a comprehensive view of how data flows across an application. 

By knowing CRUD operations, a developer will gain an understanding of: 

• MVC (Model-View-Controller) Architecture 
• REST API and HTTP Methods  
• Database Connection and Management 
• Data Mapping Between Database and Backend  
• Handling Business Logic Through Service Layers  
• Repository Patterns for Efficient Data Access

What is MVC & REST API? 

MVC controllers handle user requests and interact with the service layer to process business logic, while REST APIs expose endpoints for external systems to perform CRUD operations efficiently. Together, they enable seamless data exchange between the frontend and backend, ensuring a structured and scalable architecture. 

MVC controllers handle user requests and interact with the service layer to process business logic, while REST APIs expose endpoints for external systems to perform CRUD operations efficiently. Together, they enable seamless data exchange between the frontend and backend, ensuring a structured and scalable architecture.

Modern applications follow architectural patterns that define how data flows:

MVC (Model-View-Controller): A common design pattern that separates concerns:

• Model: Represents data (e.g., Employee entity)
• View: Displays data (e.g., HTML, React, Angular UI)
• Controller: Handles requests and calls business logic

REST API: APIs expose CRUD operations over HTTP methods:

• POST → Create
• GET → Read
• PUT/PATCH → Update
• DELETE → Delete

As shown in following Figure 1 shows the direct relationship between CRUD operations and the corresponding HTTP methods in a RESTful API. Specifically.

Example API Endpoints: 

POST /employees → Create Employee

GET /employees/{id} → Get Employee Details

PUT /employees/{id} → Update Employee

DELETE /employees/{id} → Delete Employee

What is Data? 

Before diving into CRUD, it's important to understand what data is in the context of software applications.

Data is any piece of information that applications collect, process, and store. It can be: 

• User Information (Name, Email, Password) 
• Product Details (Price, Description) 
• Transactions (Orders, Payments) 

Data is typically stored in databases — structured systems designed to organize and manage information efficiently. 

 

Ways of Data Storage 

Relational vs. Non-Relational Databases

• Relational Databases (RDBMS):  Store data in tables with predefined relationships. Examples: MySQL, PostgreSQL, Oracle.
• Non-Relational Databases (NoSQL):  Store data in flexible formats like JSON, key-value pairs, or documents. Examples: MongoDB, Redis, Cassandra. 

Understanding the type of database helps developers choose the right storage model for their applications.  

How Data is Stored in Tables  

When using a relational database like MySQL, data is stored in tables with columns and rows. Each row represents a record, and each column defines a property of that record.

Example Employee Table:

| ID  | Name      | Email           | 

|---|---------|-------------------|

| 1   | Alice     | alice@mail.com  | 

| 2   | Bob       | bob@mail.com    |