MySql Query: How can one execute two queries at the same time using mysql and java?

How can one execute two queries at the same time using mysql and java? I am facing a problem with this login i created.the login works just fine.but when it works in a network if two different uses try to login at the same instance it doesn't work. users can log in individualy.is there a particular method two achieve this?

the code is as follows

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.security.MessageDigest;
import sun.misc.BASE64Encoder;
//import java.sql.ResultSet;
import java.sql.SQLException;

public class userauthentication {

    public static String getuserauthentication(String x,String y){
String column="123",prio_no="0";
//String encrypted=password.encryptSha(x);
try{
DBFacede d=new DBFacede();
 ResultSet r1 = d.fetch("SELECT a.Password FROM login a WHERE a.user_id='"+y+"'");
            r1.last();
            int rows = r开发者_开发技巧1.getRow();
            r1.beforeFirst();

            for(int i=0;i<rows;i++){

                if(r1.next()){
                                  }

            }
column=r1.getString("Password");
 ResultSet r2 = d.fetch("SELECT a.Priority FROM login a WHERE a.user_id='"+y+"'");
            r2.last();
            int rows1 = r2.getRow();
            r2.beforeFirst();

            for(int i=0;i<rows1;i++){

                if(r2.next()){
                                  }

            }
prio_no=r2.getString("Priority");
System.out.println(column+"**********");
      }

     catch (SQLException s){
        System.out.println("SQL statement is not executed!");
      }
           //System.out.println(column);
if(column.equals(x)){
return prio_no;}
else {
return "0";
}
}

but when it works in a network if two different uses try to login at the same instance it dosnt work

The problem lies somewhere else than in the code posted as far (which is however at its own extremely poor). One possible cause is that you assigned the logged-in user as an application wide (static) variable which is shared among all clients. This way everytime when an user logs in, any previously logged-in user will be overridden with the last logged-in user.

As to your code, there's too much wrong with it that everything needs to be rewritten.

• It is not directly self-documenting.
• It is not using the right type for the value.
• It is unnecessarily firing two queries on the same table instead of one.
• It is unnecessarily shifting the resultset forth and back.
• It is prone to SQL injection attacks.
• It is leaking database resources.
• It is not handling exceptions on a sensible manner.

Here's a kickoff example of how it should be done:

public int getPriority(String username, String password) throws SQLException {
    Connection connection = null;
    PreparedStatement statement = null;
    ResultSet resultSet = null;
    int priority = 0;

    try {
        connection = database.getConnection();
        statement = connection.prepareStatement("SELECT priority FROM login WHERE username = ? AND password = ?");
        statement.setString(1, username);
        statement.setString(2, password);
        resultSet = statement.executeQuery();
        if (resultSet.next()) {
            priority = resultSet.getInt("priority");
        }
    } finally {
        if (resultSet != null) try { resultSet.close(); } catch (SQLException logOrIgnore) {}
        if (statement != null) try { statement.close(); } catch (SQLException logOrIgnore) {}
        if (connection != null) try { connection.close(); } catch (SQLException logOrIgnore) {}
    }

    return priority;
}

That's it. Here are some tutorials/articles which I strongly recommend you to get yourself through:

• Java tutorial - Trails covering the basics
• Java tutorial - JDBC basics
• SQL tutorial
• Wikipedia - SQL injections