Hi, everybody

Supose this two queries:

select * from chequescaixa where id='888516'
Returns one Row

[select * from caixamovimento where docid='888516'] &&[docid] refers to [id] in chequescaixa table
Returns Nothing

[select * from chequescaixa where id not in(select docid from caixamovimento)]
Returns Nothing

But

[select * from chequescaixa where id not in(select docid from caixamovimento where docID IS NOT NULL)]
Returns one Row

I supposed the query

[select * from chequescaixa where id not in(select docid from caixamovimento)]

should return the correct value.Is there anything I'm missing?

TIA