Clash Royale CLAN TAG

where can i write in the code to avoid duplicate byyer registration using database using jsp . i mean no multiple entries in database with same name

<%

String date="NO";

String uname= request.getParameter("uname");

String fname= request.getParameter("fname");

String lname= request.getParameter("lname");

String password= request.getParameter("pass");

String email= request.getParameter("email");

String phoneno=request.getParameter("phoneno");

String photo=request.getParameter("photo");

try

{

ResultSet rs=null;

int id=0;

int i=0;

String str="USR00";

Connection con=databasecon.getconnection();

Statement st=con.createStatement();

String qry="select max(id) from user";

rs=st.executeQuery(qry);

if(rs.next())

{

i=rs.getInt(1);

i++;

uid=str+i;

System.out.println(uid);

}


//sConnection con=databasecon.getconnection();

PreparedStatement ps=con.prepareStatement("insert into user

values(?,?,?,?,?,?,?,?,?)");

ps.setInt(1,id);

ps.setString(2,uid);

ps.setString(3,uname);

ps.setString(4,fname);

ps.setString(5,lname);

ps.setString(6,password);

ps.setString(7,email);

ps.setString(8,phoneno);

ps.setString(9,photo);

ps.executeUpdate();

System.out.println("==========PS Successfully Registered==========");

String qry1="insert into addvalet(userid,amount) values('"+uid+"','"+amt+"')";

Statement st1=con.createStatement();

st1.executeUpdate(qry1);

System.out.println("==========st1 Successfully Registered===========");

response.sendRedirect("user.jsp?m=success");

//out.print("USER REGISTERED SUCCESSFULLY");

}

catch(Exception e1)

{

out.println(e1.getMessage());

}

%>

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