One SQL to summarize different 'group by' levels

I have a Stock table in database:

Based on data in Stock Table, I want to have as output more detailed data:

Stock Qty represents the total qty in stock for Item A.

Location Qty represents the total qty for Item A for each Location

Sub Location Qty represents the total qty for Item A, for a specific location for each sub Location.

I was wondering if there is a way to get the detailed output in one query or should I make each query individually and write some code to join between each results.

I could write:

• In order to get Stock Qty:

  SELECT Item, Sum(Qty) as StockQty
  From Stock
  Group By Item;
  

• In order to get Location Qty:

  SELECT Item, Location, Sum(Qty) as LocationQty
  From Stock
  Group By Item, Location;
  

• In order to get Sub Location Qty:

  SELECT Item, Location, SubLocation, Sum(Qty) as SubLocationQty
  From Stock
  Group By Item, Location, SubLocation;
  

And then in code behind, write some code for output in a datagridview.

Actually, I am looking for a query that returns all the data in one datatable and bind it to the datagridview.

Any other solution is welcome.

I am working in AS400 but if there is a solution in others DBMS, please answered, I will try to make it work (if possible) in my DBMS environment.