compare to blank - greater or smaller?

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Posted on by ha_wai

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Hi all,

I am trying to determine if a number of times are in the right sequence. I'm doing this by:

If( time1 <= time2 && time2<=time3 && ..., sequence true, sequence false)

If all time fields are not blank this works quite fine. Unfortunately there are some use cases where not all time fields will be filled but instead left blank. The others still need to be tested for sequenceiality (is this a real english word?) In this case the above doesn't work.

Is this because blank is greater or smaller than anything non blank or because it is generally impossible to compare something to nothing?

Thanks in advance for your help and thoughts

Hansjoerg

Categories:

Building Power Apps

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rb 835 Super User 2024 Season 1 on at

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I found this interesting, so I have visualised some very explicit tests.
It is obvious that Blank() is less than any date, according to PowerApps logic. Therefore, we just need to define our own logic to say that if date N+1 is Blank(), then consider date N to be in sequence:
(DatePicker1.SelectedDate <= DatePicker2.SelectedDate || IsBlank(DatePicker2.SelectedDate)) && (DatePicker2.SelectedDate <= DatePicker3.SelectedDate || IsBlank(DatePicker3.SelectedDate))
You will, however, get true if all dates are blank. Maybe this isn't what you need, but as you can see, you have to define your own logic for dealing with Blanks.

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ha_wai 104 on at

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Thanks @metsshan
unfortunately for me PowerApps logic isn't so obvious.
If blanks would indeed be considered < non blanks just turning around the comparisons should have worked (starting with the latest time point backwards)
I've just trialled timex <= timex-1 && timex-1 <= timex-2....
If all fields are filled in it works the same as the upwards comparison but with blanks it remains false. My conclusion from that is that blanks are not really <nonblanks.

So I'll have to include testing for blank into the logic. This will make the code rather messy and long as I'm looking at 12 time points 😞

I'll keep this open for the moment and report if the combined logic works.

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ha_wai 104 on at

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@metsshan
The combined logic works, thank you very much for your help!

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