sql - ALTER/ADD COLUMN as SUM of two or more existing columns

Question

I know how to do it in creating a table but is there a way to add or update a column and set it as the sum of two or more existing columns? thank you in advance.

Answer 1

You can add a computed column:

alter table t add column sumcol as (col1 + col2);

The value is calculated when the table is queried, so it is always up-to-date.