水晶报表参数字段公式

Question

有人可以解释一下这段代码吗？ 从我们的一份客户水晶报告中找到这个

(not hasvalue({?Item Group@select ItmsGrpCod, ItmsGrpNam from OITB}) or 
if isnumeric({?Item Group@select ItmsGrpCod, ItmsGrpNam from OITB})
    then {OITB.ItmsGrpCod} = tonumber({?Item Group@select ItmsGrpCod, ItmsGrpNam from OITB})
    else true
) and
(not HasValue({?Item@Select * from OITM}) OR 
if (isnull({?Item@Select * from OITM}) or (strcmp(Minimum({?Item@Select * from OITM}),"")=0 and strcmp(Maximum({?Item@Select * from OITM}),"")=0)) 
    then true 
    else {OITM.ItemCode} = {?Item@Select * from OITM} ) and
(not HasValue({?warehouse@Select * from OWHS}) OR 
if (isnull({?warehouse@Select * from OWHS}) or strcmp({?warehouse@Select * from OWHS}[1],"")=0 )
then true
else {OITW.WhsCode} = {?warehouse@Select * from OWHS})

该水晶报告中有3个参数。 参数是项目、项目组和仓库