This program simply starts deleting records from the front of a table.  However, it gets intermittent errors saying it cannot find the row to delete even though there may be hundreds of rows left in the table.  The table does not have a primary key. 

The code contains a comment section showing the DDL for the table and a button to put 4 rows into the table.  If you start with an empty table and put 4 rows into the table, then click the 'Go' button, the failure likely will occur trying to delete the first row.  If you close the program after adding the 4 rows, restart the program and click 'Go', it will usually correctly delete all 4 rows.  With many rows in the table, it will delete some rows and then get the error. 

I have tried using a refresh after each delete, but it still fails.

I am using ibo5_10_1_b2808_Source and Embarcadero 10.3 Studio. 

[code]

unit Delete;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, IB_Components, IB_Access, IBODataset,
  Data.DB, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Query2: TIBOQuery;
    DB: TIBODatabase;
    Button2: TButton;
    Query: TIBOQuery;
    QueryNUMBER: TIntegerField;
    QueryENTERED: TDateTimeField;

    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);

  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}
{   DDL for table 'Stuff'

CREATE TABLE Stuff

(
  NUMBER          INTEGER           NOT NULL,
  ENTERED         TIMESTAMP         NOT NULL
);
}

procedure TForm1.Button2Click(Sender: TObject);
var Idx: integer;
    TS: TDateTime;
begin
  Query.Filtered := false;
  Query.Open;
  for Idx := 1 to 3 do
    begin
      Query.Append;
      QueryNUMBER.Value := Idx;
      QueryENTERED.Value := Now;
      Query.Post;
    end;
//  Duplicate record
  TS := QueryENTERED.Value;
  Query.Append;
  QueryNUMBER.Value := 3;
  QueryENTERED.Value := TS;
  Query.Post;
  ShowMessage('Added 4 rows to table.');
end;

procedure TForm1.Button1Click(Sender: TObject);
var Last_Number: integer;
begin
  Query.First;
  Last_Number := 0;
  while not Query.Eof do
    begin
      if QueryNUMBER.Value = Last_Number then
        begin
          ShowMessage('Deleting Duplicate #' + QueryNUMBER.AsString);
          Query.Delete;
          continue;
        end;
      ShowMessage('Deleting # ' + QueryNumber.AsString);
      Query.Delete;
    end;

end;

end.

[/code]