急问，数据库查询出错。解决方法

急问，数据库查询出错。
数据库条件查询，代码如下：
void __fastcall TForm1::Button1Click(TObject *Sender)
{
  int i;
  AnsiString str = "";
  if(Edit1->Text == "")
  {
  ShowMessage("请输入编号");
  return;
  }
  else
  {
  str = Edit1->Text;
  ShowMessage(Edit1->Text);
  Query1->Active = false;
  Query1->SQL->Clear();
  Query1->SQL->Add("select * from employee.db where FirstName =" + str);
  Query1->ExecSQL();
  Query1->Active = true;
  }
}
运行后,例如输入信息Kim给str令其查找FirstName为Kim的数据，提示错误信息为invalid field name Kim
请问这个错误该如何解决呢？谢谢

[解决办法]
Query1->SQL->Add("select * from employee.db where FirstName =" + str); 

改成Query1->SQL->Add("select * from employee.db where FirstName =" + QuotedStr(str));