CREATE PROCEDURE (StartDate DATE, EndDate DATE, OrderByDate BOOLEAN) RETURNS (Id INTEGER)
AS
  DECLARE Q QueryBuilder;
begin
  Q = select D.Id from Docs D where D.Processed;
  if (StartDate is not null) then
    Q.[and (D.DocDate >= :StartDate)];
  if (EndDate is not null) then
    Q.[and (D.DocDate <= :EndDate)];
  if (OrderByDate) then
    Q.[order by D.DocDate];

  for OpenQuery(Q) into :Id do
    suspend;
end

select D.Id 
from Docs D
where (D.DocDate >= :StartDate or :StartDate is null) and
         (D.DocDate <= :EndDate or :EndDate is null)

CREATE PROCEDURE GetStatistic(UserId INTEGER) RETURNS (StartDate DATE, EndDate DATE, ProcessedCount INT64, NotProcessedCount INT64)
AS
  declare Q SelectQuery;
begin
  Q = [select count(*) from Docs where DocDate between :StartDate and :EndDate];
  if (:UserId is not null) then
    Q = Q.[and where CreatedBy = :UserId];
  for select StartDate, EndDate from DateIntervals into :StartDate, :EndDate do
  begin
    open query Q.[and where Processed = True] into :ProcessedCount;
    open query Q.[and where Processed = False] into :NotProcessedCount;
    suspend;
  end;
end