JDBC Application Program

Write a program to accept rollno, name, CGPA of “n” students and store the data to a database using JDBC connectivity. Display the list of students having CGPA greater than 7. (Use MySQL /PostgreSQL).

Steps:

  1. Set up MySQL Database: Ensure MySQL is running and create a database and table.
  2. Add MySQL Connector/J: Include the JDBC driver for MySQL in your project.
  3. Java Program: Write the Java program to interact with the database.

1. Set up MySQL Database

Execute the following SQL commands to create a database and table:

CREATE DATABASE studentdb;
USE studentdb;

CREATE TABLE students (
    rollno INT PRIMARY KEY,
    name VARCHAR(50),
    cgpa FLOAT
);
2. Add MySQL Connector/J Dependency
If you are using Gradle, add the following to your build.gradle
implementation 'mysql:mysql-connector-java:8.0.33'

3.Java Program
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Scanner;

public class StudentDatabaseApp {

    // JDBC URL, username and password of MySQL server
    private static final String JDBC_URL = "jdbc:mysql://localhost:3306/studentdb";
    private static final String JDBC_USERNAME = "root";
    private static final String JDBC_PASSWORD = "password";

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        // Get the number of students
        System.out.print("Enter the number of students: ");
        int n = scanner.nextInt();
        scanner.nextLine(); // consume the newline character

        // Connect to the database
        try (Connection connection = DriverManager.getConnection(JDBC_URL, JDBC_USERNAME, JDBC_PASSWORD)) {
            System.out.println("Connected to the database!");

            // Insert student data
            String insertSql = "INSERT INTO students (rollno, name, cgpa) VALUES (?, ?, ?)";
            try (PreparedStatement preparedStatement = connection.prepareStatement(insertSql)) {
                for (int i = 0; i < n; i++) {
                    System.out.print("Enter roll number for student " + (i + 1) + ": ");
                    int rollno = scanner.nextInt();
                    scanner.nextLine(); // consume the newline character

                    System.out.print("Enter name for student " + (i + 1) + ": ");
                    String name = scanner.nextLine();

                    System.out.print("Enter CGPA for student " + (i + 1) + ": ");
                    float cgpa = scanner.nextFloat();
                    scanner.nextLine(); // consume the newline character

                    preparedStatement.setInt(1, rollno);
                    preparedStatement.setString(2, name);
                    preparedStatement.setFloat(3, cgpa);
                    preparedStatement.executeUpdate();
                }
            }

            // Query and display students with CGPA greater than 7
            String querySql = "SELECT rollno, name, cgpa FROM students WHERE cgpa > 7";
            try (PreparedStatement preparedStatement = connection.prepareStatement(querySql);
                 ResultSet resultSet = preparedStatement.executeQuery()) {
                System.out.println("Students with CGPA greater than 7:");
                while (resultSet.next()) {
                    int rollno = resultSet.getInt("rollno");
                    String name = resultSet.getString("name");
                    float cgpa = resultSet.getFloat("cgpa");
                    System.out.println("Roll No: " + rollno + ", Name: " + name + ", CGPA: " + cgpa);
                }
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Explanation:

  1. JDBC Connection: Establishes a connection to the MySQL database using the DriverManager.getConnection() method.
  2. Insert Data: Uses PreparedStatement to insert roll number, name, and CGPA of "n" students into the database.
  3. Query Data: Queries the database for students with a CGPA greater than 7 and prints their details.
  4. Exception Handling: Catches and prints SQLException in case of any database errors.
  5. Scanner: Used to read input from the user.

Make sure to replace the JDBC_URL, JDBC_USERNAME, and JDBC_PASSWORD with your actual database details. Run the program, and it will prompt you to enter student details and then display students with a CGPA greater than 7.

same program with table creation in code

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class StudentDatabase {
    public static void main(String[] args) {
        // Database connection details
        String dbUrl = "jdbc:mysql://localhost:3306/your_database_name"; // Change to your database URL
        String username = "your_username";
        String password = "your_password";

        try {
            // Load the MySQL JDBC driver
            Class.forName("com.mysql.cj.jdbc.Driver");

            // Establish the database connection
            Connection connection = DriverManager.getConnection(dbUrl, username, password);

            // Create a table (if not exists) to store student data
            String createTableQuery = "CREATE TABLE IF NOT EXISTS students (" +
                    "rollno INT PRIMARY KEY, " +
                    "name VARCHAR(255), " +
                    "cgpa FLOAT)";
            PreparedStatement createTableStmt = connection.prepareStatement(createTableQuery);
            createTableStmt.executeUpdate();

            // Insert student data (you can loop through n students)
            String insertQuery = "INSERT INTO students (rollno, name, cgpa) VALUES (?, ?, ?)";
            PreparedStatement insertStmt = connection.prepareStatement(insertQuery);
            insertStmt.setInt(1, 101); // Example roll number
            insertStmt.setString(2, "John Doe"); // Example name
            insertStmt.setFloat(3, 8.5f); // Example CGPA
            insertStmt.executeUpdate();

            // Retrieve students with CGPA > 7
            String selectQuery = "SELECT rollno, name FROM students WHERE cgpa > 7";
            PreparedStatement selectStmt = connection.prepareStatement(selectQuery);
            ResultSet resultSet = selectStmt.executeQuery();

            // Display the results
            System.out.println("Students with CGPA > 7:");
            while (resultSet.next()) {
                int roll = resultSet.getInt("rollno");
                String studentName = resultSet.getString("name");
                System.out.println("Roll No: " + roll + ", Name: " + studentName);
            }

            // Close resources
            resultSet.close();
            selectStmt.close();
            insertStmt.close();
            createTableStmt.close();
            connection.close();
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }
    }
}

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