which could be the best practice...

lets take this table for example ...

table 1 has the following column, id, description, qty, price.

I want to put a calculated field for table 1 which is the subtotal
field.

option 1. in they T_query1.sql I will put select *, "qty"*"price"
as "subtotal" from "table 1"

option 2. in they T_query1.calculated fields properties will I
declare the "subtotal" field.

option 3. Iam not so sure if this is possible, under the column
attributes I will add a new field "subtotal" then check the computed
check box.

What is the use of the computed attributes under the column
attributes besides from when we are using it for setting up a
TIB_lookupcombo

please explain the option you think is the best practice.