更新Java JDBC + mysql数据库的查询

Question

I'm trying to run update query on table doctors. The primary key of the table is defined as a composite primary key (deptid, docid). What I'm trying to do is to update field designation, qualification and time based on deptid and docid (by another query). I believe I'm doing something very silly but I'm not able to find it. Can someone help?

String did= request.getParameter("text1");
String dname = request.getParameter("text2");
String desig = request.getParameter("text3");
String qualification = request.getParameter("text4");
String time = request.getParameter("text5");

String className = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://192.168.10.13";
String user = "root";
String password = "";

PreparedStatement ps;
ResultSet rs;

try {
    Class.forName(className);                
    Connection con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/webhospital","root","");
    //        PreparedStatement prepStmt = (PreparedStatement) conn.prepareStatement("Select * from tbl_userinfo");
    ps = (com.mysql.jdbc.PreparedStatement) con.prepareStatement("update doctors set Designation=?,Qualification=?,Time= ? where deptid =? and docid IN(select docid from doctors where doctorname='dname';)");
    ps.setString(1, did);
    ps.setString(3,desig);
    ps.setString(4,qualification);
    ps.setString(5,time);
    ps.executeUpdate();
}  catch (ClassNotFoundException cx) {
    out.println(cx);
} catch (SQLException ex) {
    Logger.getLogger(MysqlInsertServlet.class.getName()).log(Level.SEVERE, null, ex);
}

Answer 1

 ps = (com.mysql.jdbc.PreparedStatement) con.prepareStatement("update doctors set Designation=?,Qualification=?,Time= ? where deptid =? and docid IN(select docid from doctors where doctorname='dname';)");
            ps.setString(1, did);
            ps.setString(3,desig);
            ps.setString(4,qualification);
            ps.setString(5,time);

You have 4 question mark but set in wrong order why you don't set like :

ps.setString(1, desig);
                ps.setString(2,qualification);
                ps.setString(3,time);
                ps.setString(4,deptId);

Supplying Values for PreparedStatement Parameters

You must supply values in place of the question mark placeholders (if there are any) before you can execute a PreparedStatement object. Do this by calling one of the setter methods defined in the PreparedStatement class. The following statements supply the two question mark placeholders in the PreparedStatement named updateSales:

updateSales.setInt(1, e.getValue().intValue()); updateSales.setString(2, e.getKey());

The first argument for each of these setter methods specifies the question mark placeholder. In this example, setInt specifies the first placeholder and setString specifies the second placeholder.

Answer 2

One change required in your query is

"where doctorname='dname';)" ==>> "where doctorname='"+dname+"';)"

Answer 3

I think without editing your code it is good to show you an simple example.

    PrintWriter out = response.getWriter();
    String Title = request.getParameter("Title");
    String Artist = request.getParameter("Artist");
    String Country = request.getParameter("Country");
    String price = request.getParameter("price");
    String Year = request.getParameter("Year");

    try {
        //loading driver 

        Class.forName("org.apache.derby.jdbc.EmbeddedDriver");

        //creating connection with the database 
        Connection con = DriverManager.getConnection("jdbc:derby://localhost:1527/sample", "app", "app");

        PreparedStatement ps = con.prepareStatement("update COMPACT_DISK set TITLE=?,ARTIST=?,COUNTRY=?,PRICE=?,YEARS=? where TITLE=?");

        ps.setString(1, Title);
        ps.setString(2, Artist);
        ps.setString(3, Country);
        ps.setString(4, price);
        ps.setString(5, Year);
        ps.setString(6, Title);
        int i = ps.executeUpdate();
        if (i > 0) {
            out.println("Compact disk successfully inserted");
        }
    } catch (Exception se) {
        out.println("Error Occured : \n" + se.getLocalizedMessage());
        se.printStackTrace();
    }