Using TQuery to perform UPDATE of db table using cppbuilder v.5

Below is a snippet I came up with to update entries in a table using
TQuery

void __fastcall executeQuery(AnsiString sqlStmt)
{
  _theQuery->Close();
  _theQuery->SQL->Clear();
  _theQuery->SQL->Add(sqlStmt);
  try
  {
    _theQuery->ExecSQL();
  }
  catch (Exception &E)
  {
    ShowMessage("Error accessing DatabaseName: " +
_theQuery->DatabaseName +
                ",  " + E.Message + "\nSQL: " +
_theQuery->SQL->CommaText);
  }

  _theQuery->Close();

Quote
}

An example of an update stmt is:
"update tabel1 set column1 = 0"

The program hangs after _theQuery->ExecSQL(); Any known reason why the
update wouldn't work?