Java JDBC – Update a Column in a Table

Java has its own API which JDBC API which uses JDBC drivers for database connections. JDBC API provides the applications-to-JDBC connection and JDBC driver provides a manager-to-driver connection. Following are the 5 important steps to connect java application to our database using JDBC.

• Registering the Java class
• Creating a Connection
• Creating a Statement
• Executing queries
• Closing connection

Note: Load mysqlconnector.jar into your program.

Steps:

• Download MySQLConnect/J (JDBC connector jar file) from the following link  https://dev.mysql.com/downloads/connector/j
• Select platform-independent in select OS option
• Copy mysql-connector-java-5.1.34-bin.jar file in your project
• Right-click on it , select Build Path-> Configure Build path -> libraries -> Add JARS
• In JAR selection window, select mysql-connector-java-5.1.34-bin.jar library under your project
• Click OK
• Create a Database, add a table with records using MySQL cmd.  

Java

// Update a Column in a Table

// dont forget to import below package
import java.sql.*;

public class Database {

    // url that points to mysql database, 'db' is database
    // name
    static final String url
        = "jdbc:mysql://localhost:3306/db";

    public static void main(String[] args)
        throws ClassNotFoundException
    {
        try {
            // this Class.forName() method is user for
            // driver registration with name of the driver
            // as argument i have used MySQL driver
            Class.forName("com.mysql.jdbc.Driver");

            // getConnection() establishes a connection. It
            // takes url that points to your database,
            // username and password of MySQL connections as
            // arguments
            Connection conn = DriverManager.getConnection(
                url, "root", "1234");

            // create.Statement() creates statement object
            // which is responsible for executing queries on
            // table
            Statement stmt = conn.createStatement();

            // Executing the query, student is the table
            // name and RollNo is the new column
            String query
                = "ALTER TABLE student RENAME COLUMN roll_no TO RollNo";

            // executeUpdate() is used for INSERT, UPDATE,
            // DELETE statements.It returns number of rows
            // affected by the execution of the statement
            int result = stmt.executeUpdate(query);

            // if result is greater than 0, it means values
            // has been added
            if (result > 0)
                System.out.println(
                    "table successfully updated.");
            else
                System.out.println("unable to update");

            // closing connection
            conn.close();
        }
        catch (SQLException e) {
            System.out.println(e);
        }
    }
}