Filtering two Arrays

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Posted on by SamMartin

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Hi Community! I am sure there is something little I am missing but the logic makes no sense on the results to me!

I have two arrays, I want to get all items that appear in Array A and not in Array B, I use a filter array and it only produces everything in Array A, even if it appears in Array B. Flow below;

Thanks in advance 🙂

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ManishSolanki 15,091 Super User 2025 Season 2 on at

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Hi @SamMartin

You need to write an expression to compare each element of Array A. Pls use expression on the life side of the condition as shown below:

Expression needs to be entered in the expression box as highlighted in the above screenshot:

item()

If this helps & solves your problem, please remember to give a 👍 and accept my solution as it will help others in the future.

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SamMartin 122 on at

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Hi @ManishSolanki 🙂
How would I go about comparing it to each value in Array B? Use an Apply for Each? I get the same issue at the end when using current item to compare, it just produces everything in one array rather than everything that isn't in the other array?

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SamMartin 122 on at

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Ignore that^ It works with just using item(), I knew it would be simple! Thanks 🙂

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SamMartin 122 on at

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@ManishSolanki Sorry to be a pain, I used this on a test flow and it worked fine. I have replicated it by just simply replacing the variables with the ones in my actual flow however I am getting a lot of values in the outputs that exists in both A & B array, I am not sure why?
The Black values were handeled correctly, however the green values (in the inputs) should not be in the outputs as they exist in both, not just one array. The compose outputs is simply used as I use a compose to union one of the arrays to remove duplicates.

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SamMartin 122 on at

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I have tried replacing all of the variables and tried swapping around the item() and outputs and still no luck, it won't produce a consistent result of items in Array A but not in Array B

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eliotcole 4,363 Moderator on at

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Hi, @SamMartin, I believe that as long as your arrays are 'simple' string arrays as you have indicated above then all you need to do is change the condition in your Filter array action to have the "List of Sharepoint" on the left and the following pasted into the right:

@{item()}

That should look something like this:

From that I got these results:

If you have trouble getting the item() in there, instead tap in the right side and go to the expression editor, and just type in the following and bosh it in:

item()

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SamMartin 122 on at

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After doing some looking, there were slight differences in the duplicating values in the arrays, capitals spaces at the start etc... Added some validation to make everything the same case and trim the values, works as expected! Thanks for the help 🙂

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eliotcole 4,363 Moderator on at

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Yeah, so what I tend to do there is to use judicious usage of trim() and either toLower() or toUpper() on both values.

Like toLower(trim(VALUE)) ... that's more difficult when you're doing an array contains kind of thing, mind.

Either way, really glad that you got there, @SamMartin !

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