Help with a formula

Hi. I’ve been trying hard to learn how formulas work. It’s not been easy. Thankfully, people are helping me here.
I have this formula that is supposed to filter all the rows with a specific date that is in another table (first picture). It’s just not working. If I had only one row in that table I would get the right result. (second picture)
What am I doing wrong?
Hope It’s understandable in portuguese.

Hey @Breno_Nunes welcome. You are right its tricky to learn the formulas, but once you start to get it, everything speeds up.

Dates and times are particularly confusing, and I’m not the definitive expert, but let me share what I think I know. Dates and times, while they can be represented separately by column types, are inextricablly linked. As in every date has a time and every time has a date. Now, you might not set a date or a time, but to the computer, it always expects it. So even if the date is not there, the computer assumes it to be the first possible date the computer can track. Every date has a time. By default this time is 12:00 AM, unless it has been set. This is the ‘smallest’ value for a date, and since every subsequent date is in the future, future dates are larger.

Coda has done a lot to simplify this, like the column types and filter wizards, and especially the `Matches()` formula (which only works with Controls). When it comes to doing formulas with dates and times you’ll want to consider the dual aspect of the date-time. In fact it is often referred to a ‘date-time’ and Coda even has a hidden formula `formatdatetime()` to work with this object.

Now you may make a formula to compare two dates, as in 1/1/2020 = 1/1/2020; it appears that it should be `true`. However if the ‘hidden-but-there’ time values don’t match, then the formula will result `false`.

You could address this by making sure both values have the same time values, but a more flexible approach (usually) is to use greater and less than ( >= and <=) to compare the time values.

For example, if you are checking against 1/1/2020, where you just type in that date value, or you reference a date column, then you can know that its time is set to 12:00AM. So any other 1/1/2020 values would be greater than or equal to the 12:00AM value which is the smallest value that 1/1/2020 could have.

Once you get it, you’ll see it makes more sense when you think about how the computer handles timestamps. When things happen in the computer, it needs to record when, so it uses a timestamp value of date and time. Coda exposes some of this with the `Created()` and `Modified()` formulas which show the timestamp value of when rows were created or modified.

This took me a bit to fully understand, so have patience with yourself and continue working and you’ll get it!

2 Likes

@Breno_Nunes, you may also use ToDate formula (and don’t forget to use CurrentValue on Filter formula)

@Breno_Nunes, você também pode usar a fórmula ToDate (e lembre-se de usar o CurrentValue na fórmula Filter)

`CurrentValue.[Data do pagamento da despesa].ToDate() = [Data do Acerto].ToDate()`

Thus, the comparison will be made only if the date is the same, regardless of the time stored in each field.

Desta maneira, a comparação será feita somente se a data for igual, independente do horário armazenado em cada campo.

2 Likes

No need for the `.ToDate()`, the issue is solely because of `Despesas extras.Data etc etc` within the filter, which is a reference to the whole column. Should be `CurrentValue.Data do pagamento etc` instead.

1 Like

Thank you all for the help.
Just found out after many trial and error that the problem was the filter formula, as always for me.

The correct formula should be:

[Despesas extras].Filter([Data do pagamento da despesa]=thisRow.[Data do acerto]).[Valor total da despesa].Sum()

I didn’t clearly understand why, though.

It seems that I have to use thisRow whenever I’m referencing each row of another table.