用滚动子总数和百分比查询

I have the following query:

我有以下查询:

select
    DrugName,
    DrugCategoryName,
    count(*) as Count,,
    'Percentage of Total' as Percentage
from
    Visit V
Inner Join Drug D on
    V.DrugID = D.DrugID
Inner Join DrugCategory DC on
    D.DrugCategoryID = DC.DrugCategoryID
where
    V.StartDate >='01 Feb 2017' and V.EndDate < '01 Mar 2017'
group by
    DrugName, DrugCategoryName
select