Помогите найти ошибки в PL/SQL функции расчёта остатков на дату : Супермаг Плюс (Супермаг 2000)

CREATE OR REPLACE FUNCTION RemainsAtDate (
  s_article IN SMCard.article%TYPE,
  s_date IN SMDocuments.createdat%TYPE,
  s_storeloc IN SMStoreLocations.id%TYPE
) RETURN SMSpec.quantity%TYPE
IS
  o_quantity SMSpec.quantity%TYPE;
BEGIN
SELECT SUM(q)
  INTO o_quantity
  FROM (
    (SELECT SMSpec.quantity AS q FROM SMSpec, SMDocuments
      WHERE
       SMSpec.doctype = SMDocuments.doctype AND
       SMSpec.docid = SMDocuments.id AND
       SMDocuments.locationto = s_storeloc AND
       SMSpec.article = s_article AND
       SMDocuments.docstate = 3 AND
       SMDocuments.createdat <= s_date
    )
    UNION ALL
    (SELECT (0 - SMSpec.quantity) AS q FROM SMSpec, SMDocuments
      WHERE
       SMSpec.doctype = SMDocuments.doctype AND
       SMSpec.docid = SMDocuments.id AND
       SMDocuments.locationfrom = s_storeloc AND
       SMSpec.article = s_article AND
       SMDocuments.docstate = 3 AND
       SMDocuments.createdat <= s_date));
  return o_quantity;
END;
/

CREATE OR REPLACE FUNCTION RemainsAtDate2 (
  s_article IN SMCard.article%TYPE,
  s_date IN SMDocuments.createdat%TYPE,
  s_storeloc IN SMStoreLocations.id%TYPE
) RETURN SMSpec.quantity%TYPE
IS
  o_quantity SMSpec.quantity%TYPE;
BEGIN
  SELECT
    (SELECT SUM(SMSpec.quantity) FROM SMSpec, SMDocuments
      WHERE
       SMSpec.doctype = SMDocuments.doctype AND
       SMSpec.docid = SMDocuments.id AND
       SMDocuments.locationto = s_storeloc AND
       SMSpec.article = s_article AND
       SMDocuments.docstate = 3 AND
       SMDocuments.createdat <= s_date
    )
    -
    (SELECT SUM(SMSpec.quantity) FROM SMSpec, SMDocuments
      WHERE
       SMSpec.doctype = SMDocuments.doctype AND
       SMSpec.docid = SMDocuments.id AND
       SMDocuments.locationfrom = s_storeloc AND
       SMSpec.article = s_article AND
       SMDocuments.docstate = 3 AND
       SMDocuments.createdat <= s_date)
  INTO o_quantity FROM DUAL;
  return o_quantity;
END;
/