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program to make start-connect by (oracle )

amit taneja
Ranch Hand

Joined: Mar 14, 2003
Posts: 810
Hi
I am only simply making the program to have output like given in this page
I have coded in core-java with database in MS-Access having "testing" as System DSN.

In database table "relation" having only two column viz "parent" and "child"

PLEASE HELP ME TO GET FIRST OUTPUT GIVEN IN THE ABOVE LINK.

I tried it but getting error
D:\java_prac>javac db/DBConnection.java
db/DBConnection.java:43: rs1 is already defined in child(int)
ResultSet rs1= stmt1.executeQuery("SELECT * from relation where
parent=0");
^
db/DBConnection.java:45: rs1 is already defined in child(int)
ResultSet rs1= stmt1.executeQuery("SELECT * from relation where
parent="+parent);
^
2 errors

D:\java_prac>




following is the java code tried

-------------------

package db;

import java.util.*;
import java.sql.*;

public class DBConnection {

public Connection getConnection()
{
Connection con =null;

String dbDriver = "sun.jdbc.odbc.JdbcOdbcDriver";
String url= "jdbc dbc:testing";
try
{
Class.forName(dbDriver);
con = DriverManager.getConnection(url);
}
catch(Exception e)
{
System.out.println("Exception caught "+e);
e.printStackTrace();
}
return con;

}

public static void main(String args[]){

DBConnection dbcon= new DBConnection();
dbcon.child(0);
}


void child(int parent) {
int a=0;
//DBConnection dbcon1= new DBConnection();
Connection con1= this.getConnection();
Statement stmt1=con1.createStatement();
ResultSet rs1=null;

if(parent==0) {
ResultSet rs1= stmt1.executeQuery("SELECT * from relation where parent=0");
}else {
ResultSet rs1= stmt1.executeQuery("SELECT * from relation where parent="+parent);
}
if(rs1.next())
{
a=rs1.getInt(2);
System.out.println('\n' +" ");
while(rs1.next()) {
a=rs1.getInt(2);
System.out.println('\n' +" ");
DBConnection dbcon1= new DBConnection();
dbcon1.child(a);
}
}
else
return;
}
}

-----------

with reference to above link I put the entries shown as insert in above link page... but instead of null i putted "0"


HELP ME TO FIGURE IT OUT


REGARDS,
AMIT


Thanks and Regards, Amit Taneja
Ernest Friedman-Hill
author and iconoclast
Marshal

Joined: Jul 08, 2003
Posts: 24187
    
  34

You only need to declare a variable once in a given method or class; after that you can refer to it without redeclaring it. To "declare" a variable, you give both its name and its type. This is a declaration:

ResultSet rs1 = null;

To refer to that variable again, you just use the name, and not the type:

rs1 = stmt1.executeQuery("SELECT * from relation where parent=0");


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