JDBC FAQ Part7

14: How to delete records from  a table  from  jdbc application?.

import java.sql.*;
public class DeleteTableEx
{
   public static void main(String[] args)throws Exception
   {
            Class.forName(“oracle.jdbc.driver.OracleDriver”);

Connection con = DriverMadoeer.getConnection(“jdbc:oracle:thin:@localhost:1521:xe”,”system”,”jhon”);

            Statement st = con.createStatement();
            int updateCount = sst.executeUpdate(“delete from emp3 where esal>=7000”);
            System.out.println(“records deleted………”+updateCount);

            con.close();
   }
}

15:What is ment by ResultSet object and How to Fetch the Data from Database?.

ResultSet:-

ResultSet is an Object which can be used to maintain the fetched data from database in the JDBC applications
       
When we execute a selection group sql query, either with executeQuety()  or with execute() automatically a ResultSet object will be created at heap memory with the fetched data from database.

• To get the ResultSet object reference directly we will use executeQuery(..).
• When we create a ResultSet object automatically a cursor will be create called as “ResultSet cursor” to read the data from ResultSet object.
• When we create the ResultSet object by default ResultSet cursor will be created before the first record.
• If we want to read the data from ResultSet object every time we need to check whether the next record is available or not. If the next record is available automatically we need to move that ResultSet cursor to next record position.
• To perform this work we will use the following method from ResultSet interface.

                        public boolean next()

• After getting ResultSet cursor to a record position then we need to get the data from respective fields of the particular record, for this we will use following method.

public xxx getXxx(int fno)
            (or)
public xxx getXxx(String fname)

            where xxx is byte, shor, int, long, float, double, char.

Eg:   while(rs.next())
            {
System.out.println(rs.getInt(1)+”   ”+rs.getString(2)+”   ”+rs.getFloat(3)+”   ”+rs.getString(4));
                        }

The following example demonstrates how to fetch the data from database through ResultSet object.

import java.sql.*;
public class FetchEx
{
   public static void main(String[] args)throws Exception
   {
            Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”);

Connection con = DriverMadoeer.getConnection(“jdbc:odbc:doe”,”system”,”jhon”);

            Statement st = con.createStatement();
            ResultSet rs = st.executeQuery(“select * from emp1”);
            System.out.println(“ENO      ENAME      ESAL      EADDR”);
            System.out.println(“********************************”);
            while(rs.next())
            {
                        System.out.println(rs.getInt(1)+””+rs.getString(2)+”   ”+rs.getFloat(3)+”              ”+rs.getString(4));
            }
   }
}