StoredProcedure Problem

[omata]

SQL-Code:

CREATE PROCEDURE MGLGETNUMBER
RETURNS (NEWNUMBER VARCHAR(10))
AS
DECLARE VARIABLE y CHAR(4);
DECLARE VARIABLE m CHAR(2);
DECLARE VARIABLE lfdnr INT;
BEGIN
  y = EXTRACT(YEAR FROM current_timestamp);
  m = EXTRACT(MONTH FROM current_timestamp);

  SELECT COUNT(*)+1 
  FROM rechnungen
  WHERE rnumber STARTING WITH :y || :m
  INTO :lfdnr;

  IF (:lfdnr < 10) THEN
    newnumber = :y || :m || '0' || :lfdnr;
  ELSE
    newnumber = :y || :m || :lfdnr;

  SUSPEND;
END