Change column type and set not null

How do you change the column type and also set that column to not null together?

I am trying:

ALTER TABLE mytable ALTER COLUMN col TYPE character varying(15) SET NOT NULL

This returns an error.

What is the right syntax?

This should be correct:

ALTER TABLE mytable
    ALTER COLUMN col TYPE character varying(15),
    ALTER COLUMN col SET NOT NULL

Also, if you want to REMOVE NOT NULL constrain in postgresql:

ALTER TABLE mytable 
    ALTER COLUMN email DROP NOT NULL;