打开一个ACCESS数据库，判断数据表是否存在？

str:string;
TableExist:boolean;
TableList:TStringList;
Tableindex:integer;
begin
  if opendialog1.Execute then
    try
    str:=opendialog1.FileName;
    ADOQuery1.ConnectionString:='Provider=Microsoft.Jet.OLEDB.4.0;Data Source='+str+';Persist Security Info=False';    TableExist := false;
       TableList := TStringList.Create();
       ADquery1.  .GetTableNames(TableList,false);
       for Tableindex:=0 to TableList.Count-1 do
       begin
         if TableList[TableIndex]='QueryTable' then
         TableExist := true;
       end;
       if TableExist then            //如果表存在，就把它删除
       begin
         ADOQuery.Close;
         ADOQuery.SQL.Clear;
         ADOQuery.SQL.Add('Drop Table QueryTable;');
         ADOQuery.ExecSQL;
       end;