I may be completely off course from where you want to get to but...
exists (select *
from TAU_TREATMENT_AUTHORIZATION t2
where t1.TAU_UID = t2.TAU_UID
and t2.TAU_LAST_UPDATE_DATE is null
group by t1.TAU_UIDDoes this get you there?
There are two kinds of light -- the glow that illuminates, and the glare that obscures. -James Thurber