Thanks - I have set up my time heirarchy Year, Period, Week and Day...
The SQL looks like:
select a12.PRD_LVL_CHILD PRD_LVL_CHILD,
max(a13.PRD_NAME_FULL) PRD_NAME_FULL,
a11.SLS_YEAR CALCDY,
a11.SLS_PERIOD CALCPR,
a11.SLS_WEEK CALCWP,
a11.SLS_DAY CALCDW,
max(a11.SLS_DATE) CALCUR...