Query doesn't working with JDBC in Java

[vinoth vino]

well i don't know about sql a lot and Now i m learning JDBC,

package demojdbc;

/**
 * JDBC Java Program
 * Database = vinoth
 * Tables = student,emp1 (Here, we are using emp1)
 * Username : root and Password : vino
 */

import java.sql.*;

class MysqlCon {
	
	public static void main(String args[]){
		
		try{
			//Registering a driver class
			Class.forName("com.mysql.jdbc.Driver");
			
			//Establishing the connection
			Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/vinoth","root","vino");
			
			//Creating statements
			Statement stmt = con.createStatement();
			
			//Creating ResultSet and stored their values here,
			ResultSet rs = stmt.executeQuery("select * from emp1");  //select name,age from emp1
			
			//Retriving the data from mysql
			while(rs.next()){
				System.out.println(rs.getInt(1)+" "+rs.getString(2)+" "+rs.getInt(3));   //rs.getString(2)+" "+rs.getInt(3);
			}
			
			//Closing the connection
			con.close();
			
		}catch(Exception e){
			e.printStackTrace();
		}
	}
}

OUTPUT
1 Vino 18
2 Mano 19
3 Gopal 24
4 Naveen 16
5 Praveen 22


My Doubt is,
1. Here, i can't get the result for query that i've documented in the ResultSet interface. i did "select name,age from emp1" but for me it gives exception...
2. Then what is the difference betweent statement and resultset ?
3. What is Query ?
4. Where these JDBC's are used in real life scenario ?
5. Here, What is the front end and back end applications ? java(JDBC) is frontend and Mysql is backend software right?

[Campbell Ritchie]

What is wrong with that oiutput? What exception? What were its message and error code? Have you read the Java™ Tutorials section about JDBC?

[vinoth vino]

package demojdbc;
 
/**
 * JDBC Java Program
 * Database = vinoth
 * Tables = student,emp1 (Here, we are using emp1)
 * Username : root and Password : vino
 */
 
import java.sql.*;
 
class MysqlCon {
     
    public static void main(String args[]){
         
        try{
            //Registering a driver class
            Class.forName("com.mysql.jdbc.Driver");
             
            //Establishing the connection
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/vinoth","root","vino");
             
            //Creating statements
            Statement stmt = con.createStatement();
             
            //Creating ResultSet and stored their values here,
            ResultSet rs = stmt.executeQuery("select name,age from emp1");  
             
            //Retriving the data from mysql
            while(rs.next()){
                System.out.println(rs.getString(2)+" "+rs.getInt(3));   
            }
             
            //Closing the connection
            con.close();
             
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

OUTPUT
java.sql.SQLException: Column Index out of range, 3 > 2.
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:998)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:937)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:872)
at com.mysql.jdbc.ResultSetImpl.checkColumnBounds(ResultSetImpl.java:764)
at com.mysql.jdbc.ResultSetImpl.getInt(ResultSetImpl.java:2471)
at demojdbc.MysqlCon.main(MysqlCon.java:31)


What's wrong with my code ?
and please clarify my doubts too

My Doubt is,
1. Here, i can't get the result for query i did "select name,age from emp1" but for me it gives exception...
2. Then what is the difference betweent statement and resultset ?
3. What is Query ?
4. Where these JDBC's are used in real life scenario ?
5. Here, What is the front end and back end applications ? java(JDBC) is frontend and Mysql is backend software right?

[Campbell Ritchie]

Are you asking for two columns and trying to read the third column?

[Liutauras Vilda]

Decrement numbers by 1, which are being passed as arguments of columns. As you been already told, your ResultSet rs contains 2 columns. Name is 1st one, Age is 2nd.

[edit]
Also, create methods to separate connection and querying. And probably for printing result.

[vinoth vino]

I m sorry i didn't see that clearly at that moment. Anyways Thanks a ton....
Please clarify these below doubts too
1. Then what is the difference betweent statement and resultset ?
2. What is Query ?
3. Where these JDBC's are used in real life scenario ?
4. Here, What is the front end and back end applications ? java(JDBC) is frontend and Mysql is backend software right?
5. Difference between ResultSet.TYPE_FORWARD_ONLY,ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.TYPE_SCROLL_SENSITIVE ?
6. Difference between ResultSet.CONCUR_READ_ONLY,ResultSet.CONCUR_UPDATABLE ? (Here, I know little bit of these concurrency of resultset. I'll tell what i knew,ResultSet.CONCUR_READ_ONLY it will read only here no modifications are performed. Then ResultSet.CONCUR_UPDATABLE means here we can modify anythings like creating table,updating table,modifying table) is this necessary to implement when creating statements ? without this what i can able to do ? Only "select query" will work or i can able to create,update,drop the table ?

I saw these resultset types and concurrency in java doc but i can't understand it clearly.Please makes me to understand it
Kindly please ignore it i need to know pleaseeeeeeee