you can create a function:
/* ************************************************** */
SET PATH "QSYS","QSYS2","QGPL" ; CREATE FUNCTION QGPL.TO_DATE ( PARAM_DATE DECIMAL(8, 0) ) RETURNS DATE LANGUAGE SQL SPECIFIC QGPL.TO_DATE DETERMINISTIC CONTAINS SQL CALLED ON NULL INPUT RETURN DATE ( CASE WHEN PARAM_DATE IS NULL OR PARAM_DATE = 0 THEN '9999-01-01' ELSE DATE ( INSERT ( INSERT ( PARAM_DATE , 5 , 0 , '-' ) , 8 , 0 , '-' ) ) END ) ; /* ************************************************** */
and use WEEK() function