Notification preferences

NotifPref.txt

 id | user |     type      | delivery 
----+------+---------------+----------
  1 |    1 | NotifReply    | Website
  2 |    1 | NotifReply    | Email
  3 |    2 | NotifRethread | Website
  4 |    3 | NotifWiki     | Website
  5 |    3 | NotifWiki     | Email

Here's one way:

select "user", type
from (
    select "user", type,  string_agg(delivery,',' order by delivery) preff
    from user_notification_pref
    group by type, "user"
) subq
where preff = 'NotifDeliverEmail,NotifDeliverWebsite';

select "user", type from user_notification_pref
group by type,"user"
having bool_or(delivery='Website') and bool_or(delivery='Email');