Assistance creating SQL query in Oracle to split by weeks
To get the week number of a date use:

to_char(sysdate, 'WW')


You can group on this:

select   to_char(ORDER.DATE, 'WW') as WEEK
         Sum(ORDER_TOTALS.ORDER_TOT_NET)  As "ORDER_TOT_NET",
         Sum(ORDER_TOTALS.ORDER_TOT_WGHT) As "ORDER_TOT_WGHT",
         Sum(ORDER_TOTALS.ORDER_TOT_QTY)  As "ORDER_TOT_QTY",    
         Sum(ORDER_TOTALS.ORDER_TOT_SQM)  As "ORDER_TOT_SQM"
From     ORDER ORDER, ORDER_TOTALS ORDER_TOTALS
Where    ORDER.ORDER_NO = ORDER_TOTALS.ORDER_NO
group by to_char(ORDER.DATE, 'WW');


Instead of WW you can also use IW. The last one gives the ISO Week. Here the beginning or the end of the year might end up in the week of the previous/next year. Look for it in Wikipedia (https://en.wikipedia.org/wiki/ISO_8601) for more information on this.