请帮我看看这段代码有什么错误?

Question

这是一个登录界面的代码,当我运行是会报错: Invalid use of keyword
                                         Token:where
                                         Line Number:1
procedure TForm1.suiButton1Click(Sender: TObject);
var db:string;
begin
db:=extractfilepath(application.ExeName);
query1.DatabaseName:=db;
query1.Close;
query1.Params.Clear;
query1.SQL.Clear;
if suicombobox1.Text='操作员' then
  query1.SQL.Add('select * from worker')
else
  if suicombobox1.Text='操作员' then
     query1.SQL.Add('select * from manager');
     query1.SQL.Add('where 工号=:num and 密码=:psw');
     query1.ParamByName('num').AsString:=suiedit1.text;
     query1.ParamByName('psw').AsString:=suiedit2.text;
     query1.Open;
if times<3 then
  if query1.RecordCount=0 then
    begin
      suimessagedialog1.ShowModal;
      times:=times+1;
      suiedit1.SetFocus;
    end
  else
     if suicombobox1.Text='操作员' then
        begin
          form1.Visible:=false;
          form2.showmodal;
          form2.FreeOnRelease;
          form1.Visible:=true;
          suiedit1.Text:='';
          suiedit2.Text:='';
          suiedit1.SetFocus;
        end
      else
       if suicombobox1.Text='管理员' then
         begin
           form1.Visible:=false;
           form3.showmodal;
           form3.FreeOnRelease;
           form1.Visible:=true;
           suiedit1.Text:='';
           suiedit2.Text:='';
           suiedit1.SetFocus;
         end
       else
         begin
         suimessagedialog3.showmodal;
         end
else
  begin
  suimessagedialog2.showmodal;
  application.Terminate;
  end;
end;

Answer 1

这样试试呢where [工号]=:num and [密码]=:psw

Answer 2

query1.SQL.Add('where 工号=num and 密码=psw');

Answer 3

你if语句有问题.
if suicombobox1.Text='操作员' then
  query1.SQL.Add('select * from worker')
else
  if suicombobox1.Text='操作员' then //是不是应该为'管理员' ?如果为管理员时,没有SELECT语句
     query1.SQL.Add('select * from manager');你这儿判断不严谨,难道只有上面2种人员角色?