我已经用java创建了一个sql登录系统，但是我想知道什么只允许帐户类型为1的人访问这个程序。我写的查询总是出现错误。课程的安全性不是一个问题，因为它只是针对课程作业

public void login(){
        try{
            int a = 0;
            int b =1;

            String query ="select * from Users where Login = '"+ 
main_menu.login_text.getText()+"' and Password='" 
+main_menu.passwordtext.getText().toString()+"' and Account Type='" +1+ 
"'" ;
            rs =st.executeQuery(query);
            System.out.println("Records from Database");
            if(rs.next()){
                f=2;

                query ="select * from Users where Login = '"+ 
main_menu.login_text.getText()+"' and Password='" 
+main_menu.passwordtext.getText().toString()+"' and Account Type='" +0+ 
"'" ;
                rs =st.executeQuery(query);
                System.out.println("Records from Database");
                }

            else if (rs.next()){
                f=1;
            }
            else{

                JOptionPane.showMessageDialog(null, "Incorrect Username 
and Password...");
            con.close();}

        } catch(Exception ex){
            System.out.println("Error"+ex);
        }