How Can You Establish A Connection To The Database?

if you are using java and oracle then by using 'thin' driver you can do a connection......

the following are the steps:-

import java.io.*;
import java.sql.*;

class Contest
  {
    public static void main(String args[])throws SQLException
{
    try
{
   Class.forName("oracle.jdbc.driver.OracleDriver");
Connection conn=DriverManager.getConnection("jdbc:oracle:thin:@192.168.0.13:1521:
ora_sid","scott","tiger");
String st="select * from emp";
PreparedStatement ps=conn.prepareStatement(st);
ResultSet rs=ps.executeQuery();
while(rs.next())
{
   String s1=rs.getString(1);
   String s2=rs.getString(2);
   String s3=rs.getString(3);
  System.out.println(s1+" "+s2+" "+s3);
}
conn.close();
}
}

/*here 192.168.0.13 is the ip-address of the machine where oracle server is installed. If your system is a stand-alone one the instead of ip-address you can give "localhost" or loop-back address "127.0.0.1", and "1521" is the default port number of connecting oracle with java..*/