Formula works most of the time but no always

[Fof_Webmaster]

When a new license plate number is entered in a new report (Form view), I want to show the dates of any matching license plates in previous reports. This needs to update without sync - the app is setup to work off-line which is the norm for our users who work in the forest.

I’ve setup a virtual column ,LongText type, with the following formula:

CONCATENATE(SELECT(NRC Reporting[Timestamp], ([License Plate #] = [_THISROW].[License Plate #])))

The expression assistant warns: “Note, this expression could significantly impact sync time.” But this works perfectly 70-80% of the time. It work off-line and doesn’t matter how many matches are found. I can’t find an underlying reason when it doesn’t work.

Any help would be appreciated.
Bob Haizmann

[Aleksi]

What is the difference when the formula works and when not?

[Fof_Webmaster]

Here’s an example using the same license plate number. In the first pic the match is not working. It returns a date that may or may not be a match and incorrectly shows a date format only. Then I entered a different license plate to reset the search input. Next for the second pic I re-entered the same license as the first pic. The the match works correctly and shows Datetime format as is expected.

[Bob_Haizmann]

Should I try a different formula or not use a virtual column? A little more clarity on the problem. When the formula doesn’t work it always brings in only one date and that date may be wrong.

Bob

[Aleksi]

When you are Online, does this functionality work always?