菜鸟的两段DELPHI窗口登陆验证代码

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var
Form1: TForm1;
count:integer;
implementation

uses unit2;

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
count:=1;
if Form1.Edit1.Text='' then
showmessage('请输入用户名!')
else if Form1.Edit2.Text='' then
showmessage('请输入密码!')
else 
begin
ADOQuery1.Close;
ADOQuery1.SQL.Clear;
ADOQuery1.SQL.Text:='select Password from logon where user='''+ trim
(EDit1.Text)+'''';
ADOQuery1.Open;
if ADOQuery1.FieldByName('Password').AsString=EDit2.Text then
begin
Form1.Hide;
Form2.show
end
else 
begin
showmessage('密码错误,请从新输入!');
inc(count);
if (count=3)then
exit
end
end
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
close;
end;

end

unit psd;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, DB, DBTables;

type
  TForm1 = class(TForm)
    Table1: TTable;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Edit1: TEdit;
    Edit2: TEdit;
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure Edit2Change(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  count:integer; //设置全程整型变量作为计数器

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
   results:variant;
begin
   if Edit1.Text=''  then
   showmessage('用户名不能为空！');
   if Edit2.Text='' then
   showmessage('请输入密码！');
   count:=count+1;//计数加1
   results:=table1.Lookup('users',Edit1.Text,'password');
   //检索数据库中对应的用户名的密码项
   if results=Edit2.Text   then
      showmessage('密码确认，即将进入学生信息管理系统。')
      //如果对应相同则进入，此处只是演示，所以只是简单说明密码确认
   else
   begin
      showmessage('错误的用户名或密码！');//密码不确认
      if(count=3) then
         close;//三次错误，强制退出
   end;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
   Application.Terminate;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
   table1.Active:=true;//窗体初始化，连接数据库
   count:=0
end;

procedure TForm1.Edit2Change(Sender: TObject);
begin
   if(Edit2.Text=#13)  then//当在edit2中输入密码后，按回车键，执行密码查询
      Button1.Click
      else
end;

end.

第一段代码 要求 数据库名取为logon
权限设定是登陆三次，密码错误报错！