postgresql7.1
select
distinct i.item_id, i.live_revision
from
cr_items i, cr_release_periods p
where
i.publish_status = 'ready'
and
i.live_revision is not null
and
i.item_id = p.item_id
and
(current_timestamp between p.start_when and p.end_when)
select
distinct i.item_id
from
cr_items i, cr_release_periods p
where
i.publish_status = 'live'
and
i.live_revision is not null
and
i.item_id = p.item_id
and
not exists (select 1 from cr_release_periods p2
where p2.item_id = i.item_id
and (current_timestamp between p2.start_when and p2.end_when)
)