31: how to update the database through PreparedStatement object.
import java.sql.*;
public class PreparedUpdateEx
{
public static void main(String[] args)throws Exception
{
Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”);
Connection con = DriverManager.getConnection(“jdbc:odbc:nag”,”system”,”durga”);
PreparedStatement pst = con.prepareStatement(“update emp1 set esal = esal+? Where esal<?”);
Pst.setInt(1,500);
Pst.setFloat(2,10000.0f);
Int count = pst.executeUpdate();
System.out.println(“no. of records updated:”+count);
}
}
32:how to fetch the data from database through PreparedStatement object.
import java.sql.*;
public class UpdateResEx
{
public static void main(String[] args)throws Exception
{
Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”);
Connection con = DriverManager.getConnection(“jdbc:odbc:nag”,”system”,”durga”);
PreparedStatement pst = con.prepareStatement(“select * from emp1 where esal<=?”);
Pst.setFloat(1,10000.0f);
ResultSet rs = pst.executeQuery();
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));
}
}
}
33:What is meant by Transaction? How it is possible to maintain Transactions in JDBC applications?
Public void setAutoCommit(Boolean b)
Where b=true connection is in auto commit
And b=false connection not in auto commit.
Public void commit()
Public void rollback()
The following example demonstrates how to maintain the transactions with atomicity property in the jdbc applications.
import java.sql.*;
public class TransactionEx
{
public static void main(String[] args)throws Exception
{
Connection con = null;
try
{
Class.forName(“sun.jdbc.odbd.JdbcOdbcDriver”);
Con = DriverManager.getConnection(“jdbc:odbc:nag”,”system”,”durga”);
con.setAutoCommit(“false”);
Statement st = con.createStatement();
st.executeUpdate(“insert into emp1 values(888,’fff’,8000,’hhh’)”);
st.executeUpdate(“update emp1 set esal = esal-500 where esal>= ‘abc’ “);
st.executeUpdate(“delete emp1 where esal<7000”);
con.commit();
}
catch(Exception e)
{
con.rollback();
System.out.println(e);
}
}
}
34:What is meant by SavePoint?How to use Savepoints in JDBC applications?
public SavePoint setSavePoint()
public void rollback(savepoint s)
public void releaseSavePoint();
Eg:
import java.sql.*;
public class SavePointEx
{
public static void main(String[] args)throws Exception
{
Connection con = null;
try
{
Class.forName(“oracle.jdbc.driver.OracleDriver”);
con = DriverManager.getConnection(“jdbc:oracle:thin:@locajhost:1521:xe”,”system”,”durga”);
con.setAutoCommit(“false”);
Statement st = con.createStatement();
st.executeUpdate(“insert into emp1 values(111,’fff’,8000,’hhh’)”);
savepoint sp= con.Savepoint();
st.executeUpdate(“insert into emp1 values(222,’ggg’,7000,’iii’) “);
con.rollback(sp);
st.executeUpdate(“insert into emp1 values(333,’hhh’,9000,’jjj’)”);
con.commit();
}
catch(Exception e)
{
con.rollback();
System.out.println(e);
}
}
}