Conte as linhas relevantes. Se apenas ename for necessário
select ename
from mytable
where event in (37,49) and date is null
group by ename
having count(*) = 2
EDITAR
Seguindo um novo conjunto de condições
select distinct ename
from mytable t1
where not exists (
select 1
from mytable t2
where t2.ename = t1.ename and t2.event in (37,49) and t2.date is not NULL)
;
