PostgreSQL create table with auto compute columns from different table columns - sql

Question

Have the following tables, and want to create table card where the columns fee is calculated as product_price.price + product_sale.b_rate
and comm computed is product_price.price - product_sale.s_rate
is there a way to autopopulate the table card when table product_sale and product_price populates.
such as create table card with computed column or function?
need help
product_sale
+---------+-------------+----+
| column | type | pk |
+---------+-------------+----+
| s_date | date | Y |
| seller | varchar(50) | Y |
| country | varchar(50) | Y |
| b_rate | float | |
| s_rate | float | |
+---------+-------------+----+
product_price
+---------+-------------+----+
| column | type | pk |
+---------+-------------+----+
| p_date | date | Y |
| product | varchar(50) | Y |
| price | varchar(50) | |
+---------+-------------+----+
card
+---------+-------------+----+
| column | type | pk |
+---------+-------------+----+
| c_date | date | Y |
| seller | varchar(50) | Y |
| country | varchar(50) | Y |
| fee | float | |
| comm | float | |
+---------+-------------+----+

Answer 1

You can have "pseudo" virtual columns, not bona fide real ones. PostgreSQL can emulate virtual columns as functions on a table (not persisted), However, There are several limitations:
Virtual columns can only depend on values on the same row of the same table and/or generic database functions, not other rows of other tables.
They are not listed automatically when using * on a select. See Emulating Virtual Columns.
They cannot be indexed. Meaning, if you want to search by them the search is less than optimal.
Now, I guess the first item is a deal breaker for you. This is not what you need.
I've used this trick quite successfully several times already.