Is that even possible in sql ?

Yes, we can do something like this

ALTER TABLE table_name ADD newcolumn_name type NOT NULL DEFAULT (0)
Go
Update table_name SET newcolumn_name = oldcolumn_name Where newcolumn_name = 0

Ok ! In any case I think alter statements are out of scope for Exposed. So you would have to do it manually

I'm also not sure that DEFAULT(0) is

default values from another column

. It's just "placeholder" value for further manual update. What you want may be handled with triggers, I guess.

DEFAULT(0) it’s just for set NOT NULL type for new column. Ok, will try, thank you.