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Count Unique Values in Rollup

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I’ve had to do this quite a few times… my old solution was:

  1. Rollup with ARRAYUNIQUE(values)
  2. Remove any trailing ','s in another column
  3. Count the remaining commas, +1

Now I do it all inside the rollup with the following snippet:

https://gist.github.com/RussellBishop/153d70be56ec5d8983439b6d9cf1279f

airtable-count-unique-array-rollup
IF((values), 

LEN(

IF(
    FIND(",", ARRAYJOIN(ARRAYUNIQUE(values), ",")&"") = 1, 
    SUBSTITUTE(ARRAYJOIN(ARRAYUNIQUE(values), ",")&"", ",", "", 1), 
        
    IF(
        FIND(",", ARRAYJOIN(ARRAYUNIQUE(values), ",")&"", LEN(ARRAYJOIN(ARRAYUNIQUE(values), ",")&"") - 1), 
This file has been truncated. show original

And yes - I’m keeping it as a Gist on GitHub for easy access. I’ll be adding more of these gems as I go.

13 Replies 13

That’s awesome. How would you address the issue if some of the values being rolled up included a comma. In my example, a corporate name that included a comma (ie ABC Widgets, Inc.)?

Oooph! Very interesting. I suppose you’d have to work from the fact that Airtable will always use a ‘,’ separator…

Perhaps you could make a column called Safe Corporate Name that replaces ','s found in your Corporate Names and replaces them with another character using SUBSTITUTE() – and then you can use this Rollup formula on that field instead.

Hope that helps.

Hey thanks for this! It’s exactly what I needed.

Just what we needed, thank you thank you

Or you could use …

COUNTALL(ARRAYUNIQUE(values))

@kuovonne I was about to throw all of my papers in the air from my desk and shout from the rooftops “She’s solved it!”

However, I’m not sure these two are doing the same thing, but I don’t know why that is. Let me demonstrate:

image

Arrayunique just uses ARRAYUNIQUE(values) to list them.

Any thoughts? Is there a tweak to yours that would work?

That does look strange.

Are you rolling up the same target field from the other table?

Do you have any blanks in the field being rolled up? (I doubt it, or there would be two commas in a row.)

What is the field type of the field being rolled up?

Slightly more concise way of counting array items.

Where [Unique Editors] is a compacted, unique, joined array.

Assumes no commas in array values

IF(
  LEN({Unique Editors}) > 0, 
  LEN(REGEX_REPLACE({Unique Editors},"[^,]",""))+1,
0)

Just returning to this – @kuovonne is 100% correct, the only addition is to add a condition in the rollup that the thing you’re looking for unique values of is not empty.

I am going to edit my post to make sure no one wastes their time on my awful, awful alternative :grinning_face_with_big_eyes:

If there might be empty values, you could use
COUNTA(ARRAYUNIQUE(values))
instead of
COUNTALL(ARRAYUNIQUE(values))

The differences between COUNTA() and COUNTALL() are documented in the formula field reference. COUNTALL() counts all values, including blanks. COUNTA() does not count blanks.

Doesn’t work:
COUNTALL(ARRAYUNIQUE(values))
for
image
Rollup fields aren’t an option for other rollups, so in my case, trying to count the unique values in the rollup field won’t work. I have the above in a formula field and it only returns a 1.

You probably need a rollup of a lookup with ARRAYFLATTEN. It is hard to tell without a deeper dive into your schema.

This is nice @Collin_Schwantes, I like the [^,]
For a rollup you’d need to convert it into a string and add the separators

IF(
  LEN(ARRAYJOIN(ARRAYUNIQUE(values),',')&"") > 0, 
  LEN(REGEX_REPLACE(ARRAYJOIN(ARRAYUNIQUE(values),',')&"","[^,]",""))+1,
0)