[DataBase] How to make a column depending on another 2...

[Dantarrix]

Well, now I want to know how to make a "c" table depending on "a" and "b" table...

So "a" + "b" = "c"
Or "a" - "b" = "c"
Or ("a" + "b")/2 = "c"

Or something like that...


Thank you...