MS SQLServer如何将两列相乘，然后将它们全部加在一起..？

Question

I'm new here. First post. I'd really appreciate some help.

I'm trying to calculate total sales for all products sold. I have a Quantity column and a Price column. I understand how to multiply these two columns, BUT I do not know how to add them all together in the same query.

Here is an example: Quantity: 2, 3, 1 Price: 2, 4, 5 I could do Quantity * Price to get: 4, 12, 5 But then how would I add 4 + 12 + 5 to get the total? I need this step to be included in the same query.

EDIT: Both the Quantity and Price columns are in the same table. SALES (Quantity, Price)

I am using Microsoft SQL-Server.

Answer 1

Example if you have one table:

SELECT dbo.orderid,
             SUM(dbo.quantity * dbo.price) AS grand_total,
        FROM ORDERITEM 

If you have two tables instead of one, then:

 SELECT oi.orderid,
         SUM(oi.quantity * p.price) AS grand_total,
    FROM ORDERITEM oi
    JOIN PRODUCT p ON p.id = oi.productid
   WHERE oi.orderid = @OrderId
GROUP BY oi.orderid

Adding all the rows (orderid numbers) up together to get a total, you would simply groupby and them select the sum value. Example below:

SELECT     Orderid, SUM(quanity) AS Expr1, SUM(price) AS Expr2, SUM(quanity * price) AS Total
FROM         dbo.mytable
GROUP BY pid
HAVING      (pid = 2)

Or this in a SQL view showing the total QTY and Price:

SELECT     Orderid, SUM(quanity) AS Quanity, SUM(price) AS Price, SUM(quanity * price) AS Total
FROM         dbo.mytable
GROUP BY pid