mysqltable7.Open;
mysqltable7.IndexName:='param';
MySQLTable7.Edit;
if MySQLTable7.findkey(['pass']) then
  begin

  end;

constructor TmySQLBlobStream.Create(Field: TBlobField; Mode: TBlobStreamMode);
var
  OpenMode: DbiOpenMode;
begin
  FMode := Mode;
  FField := Field;
  FDataSet := FField.DataSet as TmySQLDataSet;
  FFieldNo := FField.FieldNo;
  if not FDataSet.GetActiveRecBuf(FBuffer) then Exit;
  if FDataSet.State = dsFilter then
    DatabaseErrorFmt(SNoFieldAccess, [FField.DisplayName], FDataSet);
  if not FField.Modified then
  begin
    if Mode = bmRead then
    begin
      FCached := FDataSet.FCacheBlobs and (FBuffer = FDataSet.ActiveBuffer) and
        (FField.IsNull or (FDataSet.GetBlobData(FField, FBuffer) <> ''));
      OpenMode := dbiReadOnly;
    end else
    begin
      FDataSet.SetBlobData(FField, FBuffer, '');
      if FField.ReadOnly then DatabaseErrorFmt(SFieldReadOnly,
        [FField.DisplayName], FDataSet);
      if not (FDataSet.State in [dsEdit, dsInsert]) then // dsSetKey
        DatabaseError(SNotEditing, FDataSet);
      OpenMode := dbiReadWrite;
    end;
    if not FCached then
    begin
      if FDataSet.State = dsBrowse then
        FDataSet.GetCurrentRecord(FDataSet.ActiveBuffer);
      Check(Engine, Engine.OpenBlob(FDataSet.Handle, FBuffer, FFieldNo, OpenMode));
    end;
  end;
  FOpened := True;
  if Mode = bmWrite then Truncate;
end;

TmySQLBlobStream.Create(???,bmWrite)
TmySQLDataSet.CreateBlobStream(???,???)
TmySQLDataSet.SetKeyFields(???,(...))
TmySQLTable.FindKey(???)
TForm1.FormCreate(???)