用于从两个表获取数据的Java代码

Question

String pnumber = request.getParameter("pnumber");
          ResultSet rs = DAO.fetch("SELECT * FROM Products Where ProductNumber ='" + pnumber + "'");
          ResultSet r = DAO.fetch("SELECT * FROM ExpensiveProducts");

Here I am getting data from a database:

try {
            int v = Integer.parseInt(pnumber);

            if (pnumber.length() == 7) {

Data not passing going this condition?

                while (rs.next()) {
                    String pn = rs.getString(3);
                    String pqty = rs.getString(4);
                    int qty = Integer.parseInt(pqty);

                    if (pn.equals(pnumber)) {

                        if (qty > 0) {
                            response.sendRedirect("Status.jsp?Status=Available");
                        } else {
                            response.sendRedirect("Status.jsp?Status=Not Available");
                        }

                    } else {


                        while (r.next()) {
                            String epn = r.getString(3);
                            String epp = r.getString(4);
                            out.print(pnumber);
                            out.print(epn);
                            if (epn.equals(pnumber)) {
                                response.sendRedirect("Status.jsp?Status=EAvailable");
                            } else {
                                response.sendRedirect("Status.jsp?Status=E NAvailable");
                            }
                        }
                        response.sendRedirect("Status.jsp?Status=Product number not exist");
                    }

                }
            } else {
                response.sendRedirect("Status.jsp?Status=test");
            }

Answer 1

You have a loop around rs.next() - this will iterate once for each record in it.

Inside that you're looking at r.next() - how many will this be?

If they don't match up exactly, then you're going to have problems accessing your data.