Simple(?) question:
How should we update a number of related records in a loop?

As far as I understand the table "cursor" moves to the new value, does not stay in the same place in the following case:
If we have SDNr values in the table like 79,79,78 and we would like to "update FuelSDrsr set FuelSDrsr.SDNr=81 where FuelSDrsr.SDNr=79" only the first occurence with SDNr=79 will be updated.

Is it a bug or feature? I (wrongly?) believe cursor/pointer should not move to the new record while we are looping the table if we do not call SetLoopPosition, ReadFirstxxx etc.

TrHs = true;
While LoopKey("SDNr",FuelSDrsr,1,TrHs) begin
if (FuelSDrsr.SDNr!=oldNr) then begin TrHs=false; end;
if (TrHs) then begin
RecordCopy(oldFuelSDrsr,FuelSDrsr);
FuelSDrsr.SDNr=newNr;
if (RecordUpdate(oldFuelSDrsr,FuelSDrsr,false)==0) then begin end; //why this moves table pointer to new position?
end;
end;

I have looked at IVVcOKTool2.hal where we have
if (found) then begin
RecordCopy(oldTBIVr,TBIVr);
TBIVr.Invoice = IVp.SerNr;
if (RecordUpdate(oldTBIVr,TBIVr,false)) then begin end;
// StepBack(TBIVr); stops loop too quickly
end;

and result is the same: if we change project invoice number to greater one, then only the first project transaction record will be updated with the new invoice number, others will have the old (wrong) invoice number.