alter table phoneline add column mailrec varchar(3);
update phoneline set mailrec = 'no' where mailrec IS NULL;
alter table phoneline alter column mailrec set not NULL;
alter table phoneline alter column mailrec set default 'no';

alter table phoneline drop constraint phoneline_mailrec;
alter table phoneline add constraint phoneline_mailrec CHECK (mailrec IN ('yes','no'));

