Using MS SQL - 2012
I am trying to run a SQL Query that ranks rows by product id's. Then calculates a sum that represents the rows ranked less than or equal to it.
I set up a formula to do this and it works but is slow and resource expensive.

My gut feeling is there is a CTE or Rank function that would do what I want - I just don't know about it.

If a product has 4 rows, using the rank I could then recalculate a sum of lesser rows Qty's.

```
Product   Order     Qty Rank    Sum  
Apple     John      5   1       5  
Apple     Josh      2   2       7  
Apple     Jacob     1   3       8  
Apple     Jennifer  1   4       9  

```

Row 1 Sum is equal to (Row 1 Qty)  

Row 2 Sum is equal to (Row 1 Qty , Row 2 Qty)  

Row 3 Sum is equal to (Row 1 Qty , Row 2 Qty , Row 3 Qty )  

Row 4 Sum is equal to (Row 1 Qty , Row 2 Qty , Row 3 Qty , Row 4 Qty ) 

Any help on this would be much appreciated. 

Thanks in advance.
Josh