Combine the results of a sql query together in one result

Question

I have an application(C#) that manages a stock level for every storage unit. But now i want a complete overview of the stock level of every product from every stock unit together.

For example i have 50 apples (ProductID 1) in unit one and 25 in unit two and I use this query:

 select StockLevel 
   from Supply 
  where ProductID = '1' 

And put the result in a textbox it will always gives me the first stocklevel of 50 apples and not 75 .

Is there a way i can combine these results in an easy way?

Answer 1

If you want to combine , you want an aggregate function , sum in your case:

 select sum(StockLevel)
   from Supply
  where ProductID = '1' 

and get the apples being summed up: 75 which is 50 + 25

Answer 2

你可以这样尝试

SELECT (select sum(stock) from tablename where ProductID = 1) + (select sum(stock) from tablename where ProductID  =1) as result