Como trazer Valores NULL

Preciso trazer os valores NULL do select 'b_cod_leito'


select
count(l.exame)qtde,
c.reg,
l.data,
c.conv,
c.atend,
c.procedencia,
(select max(nome) from spdadpac(max(c.atend),c.reg,'T'))Pac,
(select max(nome) from tbconven where cod=c.conv)dconv,
(select max(nome) from tbproced where cod=c.procedencia)dproced,
l.exame,
l.sequencia,
b.cod_leito
from sicadate c
inner join silanexa l on(c.pront=l.pront)
and(c.reg=l.reg)
and(c.conta=l.conta)
and(c.atend=l.atend)
inner join sitabpro t on(l.ato=t.ato)
and(l.exame=t.codalf)
inner join atcabecatend a on a.id=c.id_atcabecatend
inner join tbleito b on b.id=a.id_tbleito
where l.pend_sadt='F'
and l.data between :datai and :dataf
and l.ato in (16)
group by c.procedencia,
c.atend,
c.reg,
l.data,
c.conv,
l.exame,
l.sequencia,
b.cod_leito