# How to create a collection from a property of another collection in a rule?

**URL:** <https://community.fibery.io/t/how-to-create-a-collection-from-a-property-of-another-collection-in-a-rule/2597>\
**Category:** Get Help\
**Created:** [February 28, 2022, 6:16pm UTC](https://community.fibery.io/t/how-to-create-a-collection-from-a-property-of-another-collection-in-a-rule/2597 "2022-02-28T18:16:49Z")\
**Posts on this page:** 1\
**Showing post:** 9

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**Author:** ![Chr1sG](https://sea2.discourse-cdn.com/flex020/user_avatar/community.fibery.io/chr1sg/32/3941_2.png) [@Chr1sG](https://community.fibery.io/u/Chr1sG)\
**Post date:** [March 1, 2022, 11:36am UTC](https://community.fibery.io/t/how-to-create-a-collection-from-a-property-of-another-collection-in-a-rule/2597/9 "2022-03-01T11:36:50Z")

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> [@Claude\_de\_Loupy](#):
>
> A “union” function would be way easier but, meanwhile, that works.

Indeed.

> [@How to union two list fields in the same Database?](https://community.fibery.io/t/how-to-union-two-list-fields-in-the-same-database/2467):
>
> I have two list fields in my Database: Tags and [Project Tags]. (Tags is an x:many relation and [Project Tags] is a lookup of an x:many field.) I want to combine them into a single list field [All Tags], so if (eg) Tags = (foo, bar) and [Project Tags] = (baz, bam) then [All Tags] = (foo, bar, baz, bam). Is this possible? I can’t figure out how to do it with a formula or a lookup. Extra complication: ultimately I actually want the unique set of all tags, so if (eg) Tags = (foo, bar) and [Pro…

It is on our radar.

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