delphi源码 基础源码-连接数据库，验证登录信息

procedure TForm1.Image4Click(Sender: TObject);
var
ADOQuery1: TADOQuery;
begin
{数据库操作：判断用户和密码是否正确}
if (edit1.Text<>'') and (edit2.Text<>'') then
begin
ChDir(ExtractFilePath(Application.ExeName));
ChDir('..');
ExeRoot := GetCurrentDir;
DataFile := GetCurrentDir+'\Data\dzyv1.mdb';
ADOQuery1:= TADOQuery.Create(self);
ADOQuery1.ConnectionString := 'Provider=Microsoft.Jet.OLEDB.4.0;Data Source='+DataFile+';Persist Security Info=False;';
ADOQuery1.SQL.Clear;
ADOQuery1.SQL.Add('select * from t_user where user_name="'+edit1.Text+'" and user_pass="'+edit2.Text+'" ');
ADOQuery1.Open;
if ADOQuery1.Eof then
begin
LogTimes := LogTimes+1;
if messagebox(handle,'您填写的用户或密码有错误！是否重新输入？','出错提示',mb_iconinformation+mb_okcancel)=IDcancel then application.Terminate;
if LogTimes>=3 then
begin
messagebox(handle,'对不起，登录次数超过3次，程序自动关闭！','非法登录',MB_ICONWARNING+mb_ok);
application.Terminate;
end;
end
else
begin
{用户和密码正确，登录成功}
UserType := ADOQuery1.FieldByName('user_type').AsString;
UserName := ADOQuery1.FieldByName('user_name').AsString;
LogTimes := 0;
ADOQuery1.Free;
Form1.Hide;
form2.ShowModal;
end;
end
else
messagebox(handle,'您没有填写用户和密码！','出错提示',mb_iconinformation+mb_ok)
end;