将Netbeans（JAVA）连接到MYSQL

Question

The problem is when I run this code, I always get answer COL12 instead of getting all the columns with data like I am getting in MYSQL workbench. I need to get same values. Moreover when I use this query "DELETE FROM test WHERE col1 = 2;" in netbeans I get Error Exception.

Here is my Code I wrote in Netbeans.
package sams;

import java.sql.*;  
import java.sql.Statement;
import java.sql.DriverManager;




public class Temp_Class {



public static void main(String[] args){

    try {

String query="SELECT * FROM test";
        Class.forName("com.mysql.jdbc.Driver");
        Connection con=      DriverManager.getConnection("jdbc:mysql://localhost/JavaProject", "root",  "19881990");
        Statement st=con.createStatement();
        ResultSet rs=st.executeQuery(query);
        rs.next();
        String sname= rs.getString(2);
 System.out.println(sname);
con.close();
    } catch (Exception e) {

            System.out.println("Error");

      }


    }



}

I have made table test in MYSQL Workbench, with columns="col1, col2, col3" with values="1, COL11, COL12" and "2, COL21, COL22";

This is the code I use to delete a value in DB. . . but getting Error Exception.

public static void main(String[] args){

    try {


        String deletesql="DELETE FROM test WHERE col1 = 2";

        Class.forName("com.mysql.jdbc.Driver");
        Connection con= DriverManager.getConnection("jdbc:mysql://localhost/JavaProject", "root", "19881990");
        Statement st=con.createStatement();
        ResultSet rs=st.executeQuery(select);

        Statement ds=con.createStatement();
        ResultSet dsrow=ds.executeQuery(deletesql);

        dsrow.next();
        String ds1= dsrow.getString(1);
        String ds2= dsrow.getString(2);
        String ds3= dsrow.getString(3);
        System.out.println(ds1+" "+ ds2+" "+ds3);

        con.close();
    } catch (Exception e) {

        System.out.println("Error");

    }


}

Answer 1

The reason you are getting one column is because you are fetching only one column

rs.next();
String sname= rs.getString(2);   //will give you one column

instead do

while(rs.next){                     //get all rows

 String col1= rs.getString(0);      //get column 1 of respective row
 String col2= rs.getString(1);      //get column 2 of respective row

 System.out.println(col1+" "+col2);

}

Answer 2

String sname= rs.getString(2); returns one column from the resultSet. If you want to have all columns you have to use:

String sname0= rs.getString(0);
String sname1= rs.getString(1);
String sname2= rs.getString(2);

Answer 3

I think the problem is from rs.getString(2)
Here you have just tried to get the third column. You can use rs.getString(0) and rs.getString(1) to get other values.

Answer 4

test table

col1 col2 col3

col1 1 2
col2 col11 col21
col3 col12 col22

you are queries for col1 (ie SELECT * FROM test)

String sname= rs.getString(2);
System.out.println(sname);

rs.getString(2) ie we are passing column index ie second column col2 and it prints the first value in column 2 ie 1
here 1 should be printed in reality