Article #15986: How to determine the current record number.

 Technical Information Database

TI986D.txt   How to determine the current record number.
Category   :Database Programming
Platform    :All
Product    :Delphi  All

Description:
Q:  "How can I determine the current record number for a dataset?"

A:  If the dataset is based upon a Paradox or dBASE table then 
the record number can be determined with a couple of calls to 
the BDE (as shown below).  The BDE doesn't support record 
numbering for datasets based upon SQL tables, so if your server 
supports record numbering you will need to refer to its 
documentation.

    The following function is given as part of a whole unit and 
takes as its parameter any component derived from TDataset 
(i.e. TTable, TQuery, TStoredProc) and returns the current 
record number (greater than zero) if it is a Paradox or dBASE 
table.  Otherwise, the function returns zero.


    NOTE: for dBASE tables the record number returned is always 
the physical record number.  So, if your dataset is a TQuery or 
you have a range set on your dataset then the number returned 
won't necessarily be relative to the dataset being viewed, 
rather it will be based on the record's physical position in 
the underlying dBASE table.


uses
  DB, DBTables, DbiProcs, DbiTypes, DbiErrs;

function GetRecordNumber(Dataset: TDataset): Longint;
var
  CursorProps: CurProps;
  RecordProps: RECProps;
begin
  { Return 0 if dataset is not Paradox or dBASE }
  Result := 0;
  with Dataset do
  begin
    { Is the dataset active? }
    if State = dsInactive then
      raise EDatabaseError.Create('Cannot perform this operation '+
                                  'on a closed dataset');

    { We need to make this call to grab the cursor's iSeqNums }
    Check(DbiGetCursorProps(Handle, CursorProps));

    { Synchronize the BDE cursor with the Dataset's cursor }
    UpdateCursorPos;

    { Fill RecordProps with the current record's properties }
    Check(DbiGetRecord(Handle, dbiNOLOCK, nil, 
RecordProps));

    { What kind of dataset are we looking at? }
    case CursorProps.iSeqNums of
      0: Result := RecordProps.iPhyRecNum;  { dBASE   }
      1: Result := RecordProps.iSeqNum;     { Paradox }
    end;
  end;
end;

end.



Reference:


7/16/98 4:33:58 PM
 

Last Modified: 01-SEP-99