Day-80 JDBC in Java – DEV Community

When building real-world applications, we often need to connect them with databases to store and retrieve data. In Java, this is achieved using JDBC – Java Database Connectivity.

JDBC is a standard Java API that allows applications to connect and interact with relational databases such as MySQL, PostgreSQL, Oracle, or SQL Server.

What is JDBC?

JDBC (Java Database Connectivity) is:

• A standard Java API for connecting Java applications with relational databases.
• A set of classes and interfaces provided by the Java platform.
• Useful for performing CRUD (Create, Read, Update, Delete) operations in databases.

Steps in JDBC

To connect a Java program with a database using JDBC, we follow 7 main steps:

1. Import the Package

import java.sql.*;

2. Load and Register the Driver

Each database needs a specific driver. Example for MySQL:

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

3. Establish a Connection

We connect our Java program to the database using:

Connection con = DriverManager.getConnection(
    "jdbc:mysql://localhost:3306/mydb", "username", "password");

4. Create a Statement

There are three ways to create statements:

• Statement – used for general SQL queries
• PreparedStatement – used for parameterized queries (more secure)
• CallableStatement – used to call stored procedures

Statement stmt = con.createStatement();

5. Execute the Statement / SQL Query

There are three execution methods:

1.executeQuery() → Used for SELECT queries (DQL).

   ResultSet rs = stmt.executeQuery("SELECT * FROM students");

2.executeUpdate() → Used for INSERT, UPDATE, DELETE queries (DML/DDL).

• Returns an int (number of rows affected).

   int rows = stmt.executeUpdate("INSERT INTO students VALUES(1, 'Tamil')");

3.execute() → Can run any SQL (returns true/false).

6. Process the Results

When using executeQuery(), results are stored in a ResultSet.

 while (rs.next()) {
            System.out.println(
                rs.getInt("rno") + " " + 
                rs.getString("name") + " " + 
                rs.getString("location")
            );
        }

7. Close the Connection

It’s important to close connections after use.

con.close();

Example

Here is a simple JDBC program that connects to a MySQL database, retrieves records from a table, and displays them:

package jdbcdemo;
import java.sql.*;   // 1. import the package

public class JdbcDemo {
    public static void main(String[] args) throws Exception {

        // 2. load and register the driver
        // Class.forName("com.mysql.cj.jdbc.Driver"); 

        // 3. establish a connection
        String url = "jdbc:mysql://localhost:3306/jdbcforyoutube";
        String username = "root";
        String password = "Kts@1812";
        Connection con = DriverManager.getConnection(url, username, password);

        // 4. create the statement
        Statement st = con.createStatement();

        // 5. execute the statement
        String sql = "select * from student";
        ResultSet rs = st.executeQuery(sql);

        // 6. process the results
        while (rs.next()) {
            System.out.println(
                rs.getInt("rno") + " " + 
                rs.getString("name") + " " + 
                rs.getString("location")
            );
        }

        // 7. close the connection
        con.close();
    }
}

Summary of JDBC Steps

1. Import the package
2. Load and register the driver
3. Establish a connection
4. Create a statement
5. Execute the query
6. Process the results
7. Close the connection