Help with a FILTER() expression

[jamijr]

Hello!

I’m trying to use a FILTER expression, but I don’t understand why is it giving unexpected results.

I have two tables: Sessão (with “IDSessão” and other columns) and Agendamento (with “IDAgendamento”, “IDSessão” as a reference, and other columns).

I’m setting up a workflow that will run in every update to the Agendamento table with the following condition:

COUNT(
  FILTER(Agendamento, ([IDSessão] = [_THISROW_BEFORE].[IDSessão]))
) = 0

I was expecting the filter to return 0 results, but it keeps returning a list with all the Agendamento in my sheet, without filtering anything.

Could anyone help me with this? Thanks in advance.