我的查询语句是这样的：
select a.weight_unit,tbl_workerformstore.product_allweight,tbl_workerformstore.storage_account
from tbl_workerformstore,(select tbl_headmaterial.weight_unit,tbl_workerform.abmfldid from
tbl_workerform,tbl_headmaterial where tbl_workerform.material_no=tbl_headmaterial.material_no)
as a where a.abmfldid=tbl_workerformstore.abmfldid;
我想使product_allweight=weight_unit*storage_account，用update没试出来。