SQL coding to add stock balance in JSP

I am facing some problem writing this SQL coding on adding
a stock balance record in JSP:
Below is an extract from my coding:

<html>
<head>
<title>Purchase A Stock Item</title>
</head>
<h1>Purchase A Stock Item</h1>
<body background="indtextb.jpg" bgcolor="#CCCCCC" text="#000000"
link="#3366CC"
vlink="#666666" alink="#996600">
<table border="1" width="400">
<tr>
<td><b>Item ID</b></td><td><b>Item Name</b></td>
<td><b>Item Ref</b></td><td><b>Vendor ID</b></td> <td><b>Item
Cost</b></td> <td><b>Item
Markup</b></td>
<td><b>Selling Price</b></td><td><b>Item Quantity</b></td><td><b>Re-
order Quantity</b></td>
<td><b>Description</b></td> <td><b>Action To Perform</b></td>
</tr>
<%@ page language="java" import="java.sql.*" %>
<body>
<form action="idbpurchase.jsp">
<input name="ItemID" type="text" width="30">
<input type="submit" value="Enter A Item ID To Purchase">
</form>
<% String ItemID;
ItemID = request.getParameter("ItemID");
if (ItemID == null) {
%>

<%
}

else

Class.forName("org.gjt.mm.mysql.Driver");

Connection myConn = DriverManager.getConnection("jdbc:mysql:///stock");
Statement stmt = myConn.createStatement();
String sql = "SELECT * FROM ITEM WHERE ItemID=" + ItemID;
ResultSet rs = stmt.executeQuery(sql);

if (rs != null) {

while (rs.next()) {
String ItemID2 = rs.getString("ItemID");
String IName2 = rs.getString("IName");
String IRef2 = rs.getString("IRef");
String VendorID2 = rs.getString("VendorID");
String ICost2 = rs.getString("ICost");
String IMarkup2 = rs.getString("IMarkup");
String ISellp2 = rs.getString("ISellp");
String IQty2 = rs.getString("IQty");

String ReQty2 = rs.getString("ReQty");
String IDesc2 = rs.getString("IDesc");

%>
<tr>
<td><%= ItemID2 %></td>
<td><%= IName2 %></td>
<td><%= IRef2 %> </td>
<td><%= VendorID2 %> </td>
<td><%= ICost2 %></td>
<td><%= IMarkup2 %></td>
<td><%= ISellp2 %> </td>
<td><%= IQty2 %> </td>

<td><%= ReQty2 %></td>
<td><%= IDesc2 %></td>

<td><a href='imodproc2purchase.jsp?ItemID2=<%= ItemID2 %>'>confirm
purchase ?</a></td>
</tr>

<%

} /* of while */
} /* of if */

stmt.close();

myConn.close();
%>
</table>
</table>
<a href="icontrol.html">Go back to admin control</a>
</body>
</html>

******************************************
<title>
Purchase A Stock Item
</title>
</head>
<%@ page language="java" import="java.sql.*" %>
<body>
<body background="indtextb.jpg" bgcolor="#CCCCCC" text="#000000"
link="#3366CC"
vlink="#666666" alink="#996600">
<h1>Purchase A Stock Item</h1>
<form method="post" action="iupdpurchase.jsp">
<table border="1" width="400">

<tr>
<td><b>Quantity to Purchase:</b></td><td><input name="Qtypurchase"
type="text"
width="4"</td>
</tr>

<%
Class.forName("org.gjt.mm.mysql.Driver");
Connection myConn = DriverManager.getConnection("jdbc:mysql:///stock");

Statement stmt = myConn.createStatement();

%>

<tr>
<td colspan="2">
<center>
<input name="pagemode" type="hidden" value="submit">
<input type="submit" value="Enter Quantity To Purchase">
</center>
</td>
</tr>
<%
stmt.close();
myConn.close();
%>
</table>
</form>
<a href="icontrol.html">Go back to admin control</a>
</body>
</html>

*********************************************************************
<html>
<head>
<title>
Purchase A Stock Item Processing
</title>
<body background="indtextb.jpg" bgcolor="#CCCCCC" text="#000000"
link="#3366CC"
vlink="#666666" alink="#996600">
</head>
<%@ page language="java" import="java.sql.*" %>
<body>
<%
Class.forName("org.gjt.mm.mysql.Driver");
Connection myConn = DriverManager.getConnection("jdbc:mysql:///stock");
String ItemID4 = request.getParameter("ItemID");
String IQty4 = request.getParameter("IQty3");

Statement stmt = myConn.createStatement();
int rowsAffected = stmt.executeUpdate("add Qtypurchase into IQty from
item where ItemID=" +
ItemID4);
if (rowsAffected == 1)
{
%>
<h1>Successful Update of Purchase Item</h1>
The stock item has been modified.
<p>
<a href="idbquery.jsp">See all stock items</a><br>

<a href="icontrol.html">Go back to control center</a>
<% }
else
{
%>
<h1>Sorry, purchase update has failed.</h1>
<a href="icontrol.html">Go back to control center</a>
<%
}
stmt.close();
myConn.close();
%>
</body>
</html>

This topic has been closed as it is a duplicate of a post in the JDBC forum.