Scanning is the process of sequentially reading every record in a result set or table, or every record in the range and/or filtered view of the result set or table if either a filter or a range, or both, are active. In most cases, scanning involves an initial navigation to the first record of the result set or table, followed by repeated calls to advance one record until all of the records have been visited.

Although scanning is a common task, it is important to note that it necessarily requires the client application to retrieve all of the records in the result set. This is not a problem when few records are involved, but if a large number of records are being scanned, network resources may be taxed.

 
TIP: If you are using ADS, and you must scan a large number of records, implement the operation using a stored procedure as described in Chapter 7. Scanning from a stored procedure executed from ADS requires no network resources when the server and the data are located on the same machine.
 

The following code demonstrates the scanning of an AdsTable. This code, associated with the OnClick event handler of the List Products button (shown in Figure 15-2), navigates the entire PRODUCTS table, assigning data from each record to the ProductList list box:

procedure TForm1.ListProductsBtnClick(Sender: TObject);
begin
 DataSource1.DataSet := nil;
 if AdsTable1.Active then AdsTable1.Close;
 AdsTable1.TableName := 'PRODUCTS';
 AdsTable1.Open;
 AdsTable1.First;
 while not AdsTable1.EOF do
 begin
   ProductList.Items.Add(AdsTable1.Fields[0].AsString +
     '      ' + AdsTable1.Fields[1].AsString);
   AdsTable1.Next;
 end;
 AdsTable1.Close;
end;