SQL Server/T-SQL Tutorial/Table/Computed Columns

Computed columns are (by default) virtual columns not physically stored in the table.

Their values are recalculated each time they are referenced in a query.
CREATE TABLE orders
        (orderid INT NOT NULL,
        price MONEY NOT NULL,
        quantity INT NOT NULL,
        orderdate DATETIME NOT NULL,
        total AS price * quantity PERSISTED,
        shippeddate AS DATEADD (DAY, 7, orderdate))
GO
drop table orders;
GO