In case anyone is interested in:
Született egy megoldás, most integrálom a való világba.:
with
dt AS
(
select valid_from d from t1
union
select valid_from d from t2
)
select
dt.d
, coalesce(t1.id, t2.id) as id
, t1.valid_from as date1
, t2.valid_from as date2
, t1.attr1
, t2.attr2
from dt
left outer join t1 on (dt.d >= t1.valid_from and dt.d < t1.valid_to)
left outer join t2 on (dt.d >= t2.valid_from and dt.d < t2.valid_to)
