Flow is unable to compare dates using NULL and OR

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Posted on 3 Mar 2020 15:35:19 by lcasey233

Hello,

I have a super simple flow that doesnt seem to work. Basically I am comparing two date fields, but 1 of the dates may be null.

I am using an OR condition to check if event Date is greater than the last event date OR the Last Event Date is Null.

The flow fails every time when the Last Event Date is Null. But I have setup the logic correctly and it would seem that this should work. But it fails every time the last event date is null. Why doesn't flow work as expected here?

InvalidTemplate. Unable to process template language expressions for action 'Condition' at line '1' and column '2706': 'The template language function 'greaterOrEquals' expects two parameter of matching types. The function was invoked with values of type 'String' and 'Null' that do not match.'.

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Laura3 71 on 09 Apr 2022 at 13:12:56

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Re: Flow is unable to compare dates using NULL and OR

Sorry, but this didn't work for me and my flow is almost identical. It seems to have an issue with the True part of the statement. Could you spell out the actual syntax you used for True? Sorry, I'm a novice at this.
abm abm 32,506 Most Valuable Professional on 03 Mar 2020 at 21:38:43

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Re: Flow is unable to compare dates using NULL and OR

Hi @Larry_Casey

I have created a list and added two date columns similar like yours. Assuming Event Date cannot be null then you can follow the below steps. If not change the logic similar like the empty check I am doing.

Above empty expression is as follows:

empty(items('Apply_to_each')?['Last_Event'])

You need to check the empty check first, if not check the event date > last event otherwise you get the null exception error you were getting earlier.

Here are my test results:

This is my List

Here are my flow results:

Second record index
Pstork1 67,077 Most Valuable Professional on 03 Mar 2020 at 20:34:51

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Re: Flow is unable to compare dates using NULL and OR

The problem is that if you don't set a default date on a date in SharePoint then Flow doesn't return that field in the results unless its filled in. So you can't test if the date value is Null because the field itself isn't included in the JSON results when you do a Get Item or Get Items. If you look at the JSON in your runs you'll see that the field itself is missing from some of the records. I think the only way to make this work is to default the date in SharePoint to some date in the distant past and then check against that date when you would check to see if its null. But at least if there was a date there then the field would be returned.
lcasey233 85 on 03 Mar 2020 at 16:56:42

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Re: Flow is unable to compare dates using NULL and OR

@abm I now understand what you were telling me. I did not realize I needed to use the field value in the empty string

Empty(item()?['Last_Event']) is equal to True

I am not a programmer so it took me a minute to figure out the correct syntax for empty

Thanks again!
lcasey233 85 on 03 Mar 2020 at 16:53:46

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Re: Flow is unable to compare dates using NULL and OR

All,

I have found the solution and really appreciate all your assistance and help. Everyone here contributed to finding the answer. I am not a programmer so this is all really new to me and now it makes sense. There is no Power Automate outage 😉

I had to use the following which was mentioned, but I didn't realize I needed to add the field value to empty.

Empty(item()?['Last_Event']) is equal to True

So the condition looks like this:
ChristianAbata 8,949 Most Valuable Professional on 03 Mar 2020 at 16:36:25

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Re: Flow is unable to compare dates using NULL and OR

@Larry_Casey could please you copy an paste what is inside of get items?
lcasey233 85 on 03 Mar 2020 at 16:29:01

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Re: Flow is unable to compare dates using NULL and OR

No matter what I try, Even if I remove the OR, Flow can not determine if a date field is empty.

This must be an Outage. I encourage anyone in this forum to try and you will see.

Simply create two date Fields in a SharePoint List.
Name them: Event_Date and Last_Event_Date (They are date fields)
Leave the Last_Event_Date empty
Then try to determine if the Last_Event_Date is empty.

Last_event_Date is empty, null, blank, string(null) etc...... I have ran through every single possible combination and flow will never recognize that a date field is empty. It returns false every single time.
lcasey233 85 on 03 Mar 2020 at 16:16:19

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Re: Flow is unable to compare dates using NULL and OR
lcasey233 85 on 03 Mar 2020 at 16:13:50

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Re: Flow is unable to compare dates using NULL and OR

How can I check for empty like that in the OR condition?

Basically I just need to know whether the Last_Event_date is empty OR the Event_Date is Greater than or equal to the Last_Event_Date.

Then apply an action if True.
abm abm 32,506 Most Valuable Professional on 03 Mar 2020 at 16:06:54

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Re: Flow is unable to compare dates using NULL and OR

Hi @Larry_Casey

You need to check empty check like this.