exists and is not null equivalence in query

Hi,

In some code I am taking over, I found this query:

select count(t.trame_id) as count, v.voiture_num as voitureNum from
arch_trames t left join voiture v on (v.tag_id=t.tag_id)
where
(t.recept_time >= 1243509320691)
and exists (select v2.voiture_num from voiture v2 where v2.tag_id=v.tag_id)
group by v.voiture_num order by v.voiture_num

Am I right that I can replace the "and exists..." clause by
"and v.voiture_num is not null " in this case?

Thanks

Raphaël

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