The BDE called FetchAll before calling RecordCount, IBX datasets do not. Call TDataSet.FetchAll before using TDataSet.RecordCount. FetchAll actually downloads all the records locally and counts them, for large tables and result sets, this can be undesirable. A faster, server side way, of accomplishing the same task is to use two select statements:

  IBQuery .SQL.Clear;   IBQuery .SQL.Add('select count(ANYFIELD) FROM YOURTABLE');   IBQuery .Open;

You can access the RecordCount by   IBQuery .FieldByName('COUNT').AsInteger;