Introduction to JDBC in Java

JDBC (Java Database Connectivity) is a Java API that allows Java applications to interact with relational databases such as MySQL, PostgreSQL, Oracle, and more. It enables you to perform SQL operations like SELECT, INSERT, UPDATE, and DELETE directly from your Java code.

JDBC acts as a bridge between your Java program and the database server, allowing you to connect, query, and manage data easily and securely.

Establish a database connection using DriverManager
Execute SQL queries using Statement or PreparedStatement
Retrieve data using ResultSet
Handle exceptions and manage transactions efficiently

Prerequisites

Before running JDBC programs, make sure you have the following installed and configured:

MySQL Database – Download MySQL
JDBC Driver for MySQL – Download MySQL JDBC Driver
MySQL Server Running
Database and Table – Create a database named studentdb and a table named students.

SQL to create database and table:

CREATE DATABASE studentdb;
USE studentdb;

CREATE TABLE students (
  id INT PRIMARY KEY AUTO_INCREMENT,
  name VARCHAR(100)
);

INSERT INTO students (name) VALUES ('Aryan'), ('Riya'), ('Amit');

Sample Data in `students` Table

+----+--------+
| id | name   |
+----+--------+
| 1  | Aryan  |
| 2  | Riya   |
| 3  | Amit   |
+----+--------+

Example: Connect to MySQL using JDBC

import java.sql.*;

public class JdbcExample {
  public static void main(String[] args) {
    try {
      Class.forName("com.mysql.cj.jdbc.Driver");
      Connection con = DriverManager.getConnection(
        "jdbc:mysql://localhost:3306/studentdb", "root", "your mysql password"
      );
      Statement stmt = con.createStatement();
      ResultSet rs = stmt.executeQuery("SELECT * FROM students");

      while (rs.next()) {
        System.out.println(rs.getInt(1) + " " + rs.getString(2));
      }

      con.close();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

This code connects Java to a MySQL database and fetches records from the students table.

यह कोड Java को MySQL database से कनेक्ट करता है और students टेबल से डेटा प्राप्त करता है।

JDBC Code Explanation (Step by Step)

Let's understand each line of the example code:

`Class.forName("com.mysql.cj.jdbc.Driver");`

Loads the MySQL JDBC driver so that Java can communicate with the database.

`DriverManager.getConnection(...)`

Creates a connection to the studentdb MySQL database.

studentdb नामक MySQL डेटाबेस से कनेक्शन बनाता है।

`Statement stmt = con.createStatement();`

Creates a Statement object to send SQL queries.

Statement ऑब्जेक्ट बनाता है जो SQL queries भेजने के लिए प्रयोग होता है।

`ResultSet rs = stmt.executeQuery(...)`

Executes the SQL SELECT query and returns a ResultSet with the data.

SQL SELECT query को execute करता है और डेटा के साथ ResultSet लौटाता है।

`while (rs.next())`

Iterates through the ResultSet to read the data.

ResultSet में डेटा पढ़ने के लिए लूप करता है।

`con.close();`

Closes the database connection to free resources.

Summary:

Driver Loading: Loads the JDBC driver.
Database Connection: Connects to the database.
Statement: Prepares SQL queries.
Query Execution: Runs SELECT queries and returns results.
Result Processing: Reads data from ResultSet.
Connection Close: Releases resources.

Expected Output

1 Aryan
2 Riya
3 Amit

This output shows the records fetched from the students table using JDBC.

यह आउटपुट JDBC की मदद से students टेबल से प्राप्त किया गया डेटा दिखाता है।

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Introduction to JDBC in Java

Prerequisites

SQL to create database and table:

Sample Data in students Table

Example: Connect to MySQL using JDBC

JDBC Code Explanation (Step by Step)

Class.forName("com.mysql.cj.jdbc.Driver");

DriverManager.getConnection(...)

Statement stmt = con.createStatement();

ResultSet rs = stmt.executeQuery(...)

while (rs.next())

con.close();