使用两列计算总金额，百分比是多少？

Question

I have built a table that includes various items, item id's and prices etc - I also have a list of stored customers on my database and the items that they bought.

I would like to be able to calculate my total VAT (16%) for these items, only the ones sold (not unsold items).

I tried this code:

SELECT sum(items.price*sales.amount) as 'Total Sold', sum((items.price*sales.amount)*0.16) AS 'Estimated Total Vat Amount'
FROM sales

But the result that followed was an 'unknown column' although it does exist. On looking online is encourages me to use an 'inner join' but if possible I would prefer to use something else..

Is that possible? if so, what could I use to get my result?

Thanks.

Answer 1

You need to join items table.

SELECT 
    sum(items.price*sales.amount) as 'Total Sold'
   ,sum((items.price*sales.amount)*0.16) AS 'Estimated Total Vat Amount'
FROM 
    sales
INNER JOIN
    items
ON
    sales.item_id=items.id