JDBC; JSP; mySQL; UPDATE: Failure to update record

The primary key is auto-incremented. I use result = ps.getGeneratedKeys(); to
obtain it and fail to update a record with the obtained primary key.

Here is the error message:
SQLException: Column not found,  message from server: "Unknown column 'thePK' in 'where clause'"
SQLState: S0022
VendorError: 1054

Here is the table:
mysql> DESCRIBE patient;
+----------------+---------------------+------+-----+---------+----------------+
| Field          | Type                | Null | Key | Default | Extra          |
+----------------+---------------------+------+-----+---------+----------------+
| patient_id     | bigint(20) unsigned |      | PRI | NULL    | auto_increment |
| address_id     | bigint(20) unsigned |      | PRI | 0       |                |
| diagnosis_id   | bigint(20) unsigned |      | PRI | 0       |                |
| sdp_id         | bigint(20) unsigned |      | PRI | 0       |                |
| firstname      | varchar(20)         | YES  |     | NULL    |                |
| middlename     | char(1)             | YES  |     | NULL    |                |
| surname        | varchar(20)         | YES  |     | NULL    |                |
| date_birth     | date                | YES  |     | NULL    |                |
| gender         | varchar(10)         | YES  |     | NULL    |                |
| occupation     | varchar(15)         | YES  |     | NULL    |                |
| marital_status | varchar(10)         | YES  |     | NULL    |                |
| num_dependants | int(11)             | YES  |     | NULL    |                |
| patient_number | int(11)             | YES  |     | NULL    |                |
+----------------+---------------------+------+-----+---------+----------------+
13 rows in set (0.00 sec)

Here is the database handler: I'd appreciate answers also to comments marked Q: in the code

package patient.patientServlets;

import java.io.*;
import java.net.*;

import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
import java.sql.*;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

import patientBeans.PatientFormBean;

public class DBHandlerPatient extends HttpServlet {
 
    public void doPost (HttpServletRequest request,
      HttpServletResponse response) {
      try { // OBTAIN A DATABASE CONNECTION
         
          // Step 1: Load the JDBC driver          
          Class.forName("com.mysql.jdbc.Driver");
             
          // Step 2: Establish a connection to the database
          Connection conn = DriverManager.getConnection(
          "jdbc:mysql://localhost/rtpmKenyaDB","rmwijage", "Psa23v1");
          String sql = null;
          sql = "INSERT INTO patient( patient_id, address_id, " +
          "diagnosis_id, sdp_id, firstname, middlename, surname, " +
          "date_birth, gender, occupation, marital_status, " +
          "num_dependants, patient_number)" +
          "VALUES ( ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
         
          PreparedStatement ps = conn.prepareStatement(sql);
         
          // Retreave bean properties to be inserted into table patient
          PatientFormBean f = (PatientFormBean) request.getAttribute("formHandler");
         
          String fname = f.getFirstName();
          String mname = f.getMiddleName();
          String lname = f.getLastName();
          String birthdate = f.getDateOfBirth();
          String theGender = f.getGender();
          String theOccupation = f.getOccupation();
          String theStatus = f.getMaritalStatus();
          String theDependants = f.getNumOfDependants();

        // Set the parameters in the prepared statement
          ps.setNull(1,Types.BIGINT); // For PRIMARY KEY generation with auto increment!
          ps.setInt(2, 0); // SQL BIGINT. Later to be given value from another table
          ps.setInt(3, 0); // SQL BIGINT.        = " =
          ps.setInt(4, 0); // SQL MEDIUMINT      = " =
          ps.setString(5, fname);
          ps.setString(6, mname);
          ps.setString(7, lname);
          ps.setString(8, birthdate);
          ps.setString(9, theGender);
          ps.setString(10, theOccupation);
          ps.setString(11, theStatus);
          ps.setString(12, theDependants);
          ps.setInt(13, 0); // This value is to be updated shortly.
       
          // Insert the row (record) into the table
          int inserted = ps.executeUpdate(); // WORKS OK
          System.out.println(inserted); // Q: Can't see result in o/p window of NetBeans IDE. Why?

          /* Query the database for the last inserted id. In this case,
           * the value of patient_id hich was allocated automatically by
           * the database
           */
        // Q: Are the following lines OK for obtaining the generated Primary Key?
          ResultSet result = null;
          int thePK = -1;
          result = ps.getGeneratedKeys();
          if (result.next()) {
          thePK = result.getInt(1);
          }
          else {
            // throw an exception from here
          }
          System.out.println(thePK);
          result.close();

        // UPDATING row in table patient. I want to have patient_number = patient_id
        // Q: According to error message, here is the culprit. But isn't patient_id = thePK?
          sql = new String("UPDATE patient SET patient_number = thePK " +
                                  "WHERE patient_id = thePK");
         
          ps = conn.prepareStatement(sql);
          int update_count = ps.executeUpdate();
          System.out.println(update_count);
         
           /* Later, I might want to have patient_number different from
            * patient_id but derived from it.
            */
           
          // Now close the connection    
          ps.close();
          conn.close();
 
      }
      catch (SQLException e) {
          // handle any errors
          System.out.println("SQLException: " + e.getMessage());
          System.out.println("SQLState: " + e.getSQLState());
          System.out.println("VendorError: " + e.getErrorCode());
          }
      catch (Exception e) {
      e.printStackTrace();
      }
     
      // Send the request to rtpm_address.html  
      try {
          getServletConfig().getServletContext().
        //  getRequestDispatcher("/success_patient.jsp").
            getRequestDispatcher("/success_patient.jsp"). // later dispatch
             forward(request, response);             // to rtpm_address.html
      }
      catch (Exception e){}
   }
}



// I do appreciate your expert advise. Thank you.