CRUD Operations

1. What are CRUD Operations?

CRUD stands for Create, Read, Update, and Delete — the four basic operations performed on data stored in a database, corresponding to SQL commands INSERT, SELECT, UPDATE, and DELETE.

2. Why is it used?

Almost every application that uses a database needs to perform these four fundamental actions on its data — adding new records, viewing existing ones, modifying them, and removing them when no longer needed.

3. Real-Life Example

Think of managing a library's book records: adding a new book (Create), searching for a book (Read), updating a book's availability status (Update), and removing a book that's no longer part of the collection (Delete).

4. Syntax

java
// Create
"INSERT INTO table (col1, col2) VALUES (?, ?)"
// Read
"SELECT * FROM table WHERE condition"
// Update
"UPDATE table SET col1 = ? WHERE condition"
// Delete
"DELETE FROM table WHERE condition"

5. Example Program

java
import java.sql.*;

public class CrudDemo {
    public static void main(String[] args) throws SQLException {
        Connection conn = DriverManager.getConnection(
            "jdbc:mysql://localhost:3306/schooldb", "root", "password"
        );

        PreparedStatement insert = conn.prepareStatement(
            "INSERT INTO students (name, age) VALUES (?, ?)"
        );
        insert.setString(1, "Kabir");
        insert.setInt(2, 20);
        insert.executeUpdate();

        System.out.println("Student record created successfully.");
        conn.close();
    }
}

Output:

Student record created successfully.

6. Key Points to Remember

• executeUpdate() is used for INSERT, UPDATE, and DELETE; executeQuery() is used specifically for SELECT.
• CRUD forms the foundation of almost every data-driven application, from simple apps to large enterprise systems.
• Using PreparedStatement for all CRUD operations is the safer, recommended practice.