How to select from an expression in SQL?

I’m really new to SQL and quite struggling with this. I have 2 tables

• MATERIAL (CODE, NAME, BUYPRICE)
• BILL (CODE, DETAIL, AMOUNT)

I want to return a new temporary column TOTALMONEYTOPAID which is BUYPRICE * AMOUNT.

Query:

SELECT 
    TOTALMONEYTOPAID 
FROM
    MATERIAL, BILL 
WHERE
    TOTALMONEYTOPAID = BUYPRICE * AMOUNT

This obviously doesn’t work.

I searched around for something like declare @variable but I don’t know how to use it. Many thanks with your answer.

Answer

This should be a really simple query:

select Material.Code, Name, Detail, BuyPrice*Amount as TotalMoneyPaid
from Material
join Bill on Bill.Code=Material.Code