Lookup column - value only once

1

Hi
I’m trying to build something fairly simple but I can’t find a way to set it up.
A table with a lookup column where you can’t set the same value twice in two different rows
I’ve tried to set up a custom filter in the lookup options, but I can’t understand how to do it
Help much appreciated thank you

2

Hi mate,

my suggestion :slightly_smiling_face:

For my example I use a task and a project table, assuming for your example that a project can have only one task :wink:

  • I assume you have a main table, with a project lookup, and a project table OK?
  • Start to create a column “Related Task” in project table, to check if a task is already linked to the lookup. In my example the formula would be [Task Test].Filter(Project=thisRow).Count()

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  • Then, in the task table, for project lookup option, you can make a custom filter, to select only project with related task = 0

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Is that OK for You ?

2 Likes
3

That is so clever, works totally! thanks for the quick response!
Have a great day!

1 Like
4

Quite simple, but we just need to have the idea !
I let you make this post as solved :wink: !

5

How do I do that :slight_smile: ? damn sorry for asking, I’ve looked around for a checkbox, tag, dropdown, whatever and searched the forum, but I can’t find how to do this.

6

Ahah that’s indeed a good question :smiley:

7

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