# How to join two rollup column to a single array and filter out duplicate values?

**URL:** <https://air.tableforums.com/t/how-to-join-two-rollup-column-to-a-single-array-and-filter-out-duplicate-values/1107>\
**Category:** Airtable Questions\
**Created:** [February 29, 2024, 4:44pm UTC](https://air.tableforums.com/t/how-to-join-two-rollup-column-to-a-single-array-and-filter-out-duplicate-values/1107 "2024-02-29T16:44:44Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![KTrager](https://avatars.discourse-cdn.com/v4/letter/k/ccd318/32.png) [@KTrager](https://air.tableforums.com/u/KTrager)\
**Post date:** [February 29, 2024, 4:44pm UTC](https://air.tableforums.com/t/how-to-join-two-rollup-column-to-a-single-array-and-filter-out-duplicate-values/1107/1 "2024-02-29T16:44:44Z")

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I’m using my airtable to attached keywords images.

I have one big keywords table with multiple categories of different keywords. Then i have multiple linked columns to the different categories. However some of the keywords overlap into different categories.

So I thought I could rollup all my linked columns and do something like this:

ARRAYUNIQUE(ARRAYJOIN(ARRAYJOIN({RollUp1}) & IF({RollUp2}, ‘,’ & ARRAYJOIN({RollUp2})) & IF({RollUp3}, ‘,’ & ARRAYJOIN({RollUp3}))))

However I still have duplicates of keywords in my final array.

After that I tried to make every possible combination of

ARRAYUNIQUE(ARRAYFLATTEN(ARRAYJOIN(Values)))

But still the same.

I’ve also tried to change my rollups to lookups, but no luck either.

I have the feeling that it’s something to do with how I try to join the three columns that might be the issue.

Does anyone know how I can join my rollups and then filter out all the duplicates?

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**Author:** ![Kuovonne](https://yyz1.discourse-cdn.com/flex029/user_avatar/air.tableforums.com/kuovonne/32/17_2.png) [@Kuovonne](https://air.tableforums.com/u/Kuovonne)\
**Post date:** [February 29, 2024, 5:17pm UTC](https://air.tableforums.com/t/how-to-join-two-rollup-column-to-a-single-array-and-filter-out-duplicate-values/1107/2 "2024-02-29T17:17:17Z")

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There is no practical way to do this with formula fields. When you use ARRAYJOIN() or the & operator, the end result is a text string, and not an array. Thus ARRAYUNIQUE() no longer sees the individual items that were in the original array; it only sees the single text string. ARRAYUNIQUE() also only acts upon the first parameter, so including different arrays as different parameters doesn’t work either.

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**Author:** ![KTrager](https://avatars.discourse-cdn.com/v4/letter/k/ccd318/32.png) [@KTrager](https://air.tableforums.com/u/KTrager)\
**Post date:** [February 29, 2024, 8:16pm UTC](https://air.tableforums.com/t/how-to-join-two-rollup-column-to-a-single-array-and-filter-out-duplicate-values/1107/3 "2024-02-29T20:16:04Z")

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Thank you for confirming this @Kuovonne