>Hi
>
>I need the records for dStart only, if tdStart is empty, I need all records, not only empty(dStart)

From the name dStart I figured you are selecting with >=, not just =, but in that case you should use date range, i.e. ...where dstart between tdStart1 and tdStart2, and if you want to select independent on dates, put tdStart1={} and tdStart2={^9999/12/31}.