如何从 ORACLE 数据库中显示 Netbeans 中 2 个表中的数据

Question

I don't know how to properly display data from 2 tables in the TextArea field. I added 2 rows in the database tables but the program displays 4 rows in the textArea instead of 2(duplicate), if I add 3 rows program displays 3xfirst row,3x second row,3x third row...etc.This is my code. Please help me in some way :(

    jTextArea1.setText(null);
    Connection connection=null;
    try
    {  
        String driverName="oracle.jdbc.driver.OracleDriver";
        Class.forName(driverName);

        String serverName = "193.2.139.xxx";
        String portNumber = "1521";
        String sid = "ers";
        String url = "jdbc:oracle:thin:@"+serverName+":"+portNumber+":"+sid;
        String username = "xxxxxxxx";
        String password = "xxxxxxxxxx";

        connection = DriverManager.getConnection(url, username, password);
        java.sql.Statement select = connection.createStatement();

        int id;
        String name; //column from table narocnik
        String surname; //column from table narocnik
        String address; //column from table narocnik
        String telephone; //column from table narocnik
        String date; //column from table prevoz
        String od; //column from table prevoz
        String v; //column from table prevoz
        String odhod; //column from table prevoz
        String cena; //column from table prevoz
        ResultSet rs1=select.executeQuery("select * from narocnik,prevoz");
        while(rs1.next()){
            id=rs1.getInt("id");
            name=rs1.getString("name");
            surname=rs1.getString("surname");
            address=rs1.getString("address");
            telephone=rs1.getString("telephone");
            date=rs1.getString("date");
            od=rs1.getString("od");
            v=rs1.getString("do");
            odhod=rs1.getString("odhod");
            cena=rs1.getString("cena");
            jTextArea1.append(name+", "+surname+", "+address+", "+telephone+", "+date+", "+od+", "+v+", "+odhod+", "+cena+"\n");
        }
        connection.close();       
    }
    catch(ClassNotFoundException e)
    {
        JOptionPane.showMessageDialog(this,"Ni gonilnika! "+e);
    }catch(SQLException e){
        JOptionPane.showMessageDialog(this,"Napaka pri povezavi! "+e);
    } 

Answer 1

Problem is in your SQL Query;

ResultSet rs1=select.executeQuery("select * from narocnik,prevoz");

If you want to join two tables you should use joining like inner join, left join, right join or outer join. But when you just use comma (,) in your query to join two tables it will be outer join. It will give you multiple result;

User Inner Join like -

Select * from table1 inner join table2 on table1.id = table2.id;

Hope it will work for you.