Merging CSV files - array aggregators or iterators?

[Boschung]

What is your goal?

I want to merge two CSV files to create a third one. Before merging, I need to adapt (create CSV) both files.
Normally, my files should have the same number of rows, but in the worst case, I might have different number of rows.

What is the problem?

If I parse 2 CSV files, running the sequence will end up in one action on the second file for each bundle of the first file.
Using array aggregators after each CSV>Create CSV modules avoids this effect, but I don’t know how to merge the two arrays into one array. Here, I can have only two tables one over each other (the second table would be added after the last row of the first table) instead of having the second table next to the first one (having a line by line merge of the data).

What have you tried so far?

Put Array Aggregators after each Create CSV.

Screenshots: scenario setup, module configuration, errors

[samliew]

Welcome to the Make community!

If you simply want to append the contents of one after the other, a CSV is basically a huge text file, so you can just map one after the other. I’m guessing this is not what you want?

I think this question is not possible to answer accurately without knowing how both output CSVs look like, and an example of how you want to “merge” them together.

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[Boschung]

Thank you for your reply!

Here is my scenario:

The first two rows of the first CSV file including the headers looks like this after the array aggregator [55]:

“valid”;“Td”;“Ts”;“FF”;“DD”;“N”

“202512120100”;“8.3”;“9.7”;“3.6”;“143”;“8”

The first two rows of the second CSV file including the headers looks like this after the array aggregator [57]:

"T";"WX";"RR";"GLO"

"11.7";"00";"0.0";"3348"

To get the combined CSV in the FTP folder [59], I have the following statement:

This is NOT what I would like to have.

My wish would be to have the combined CSV with the following output:

"valid";"Td";"Ts";"FF";"DD";"N";"T";"WX";"RR";"GLO"

"202512120100";"8.3";"9.7";"3.6";"143";"8";"11.7";"00";"0.0";"3348"

[Donald_Mitchell]

Hi @Boschung, one of your issues here is that the data collections don’t share a common key.

Are you assuming that both files have exactly the same number of rows and each row number in one goes with the data in the same row in the other file?

Either way, the process is going to pretty much be the same with just one slight difference.

Are you able to answer which joining method you’re using and can you provide sample CSV files so we can build this out and share the blueprint with you? Unfortunately we can’t share data structures, but we can share a walkthrough on that.

Essentially, you can convert both CSV files to array objects, iterate through one, then aggregate into one big array consisting of all the fields, using fields in one array to look up fields in the other.

Here’s the general flow:

Start by placing an array aggregator or Create CSV (Advanced) module, create a custom Data Structure for it consisting of all the fields from both files, put this aside. Call it Array Aggregator #3 (or Create CSV).

FTP Get a File #1 → Parse CSV #1 → Array Aggregator #1 → FTP Get a File #2 → Parse CSV #2 → Array Aggregator #2 → Iterator Array #1 → Aggreagtor Array #3 or Create CSV

For each iteration of array #1, you’ll need to place those values in their corresponding fields in array aggreagtor #3 or Create CSV.
For the fields from Array #2, you can use map() to get the value from array #2 and use the Bundle Order Position or another value as the lookup key.

Hope that makes sense and hope it helps!

If these terms don’t make sense to you, please check out Make Academy to get the basics down.

[Boschung]

Hello and thank you for your answer!

I can share two examples of CSV files used in this scenario:

Test_File_Solar.csv (1.1 KB)

Test_File_Runway.csv (2.1 KB)

Here is also the Blueprint:

Merger_CSV_files_blueprint.json (21.0 KB)

I probably miss something in the Create CSV module, to be able to get the final combined CSV file.

I’m sure that I’m close to the solution, and am really grateful for your help!

[Boschung]

I’m still struggling with the map() fonction. In the last CSV>Create CSV module, I have the following fields:

I suppose that the mapping does not work like this.

If I try with this:

, I will have the same value on all rows.

Any idea?

[Stoyan_Vatov]

What are you trying to map in there? Cause that formula isn’t going to give you anything useful. You can hover over the formula to see what argument goes in which position.

[Donald_Mitchell]

You’re getting close. You don’t need map(), just get(). You’ll see in the blueprint.

I just set this up and here’s an example of the output

Here’s the scenario Combine CSV by Row Number - Make.com Automation Scenario

You’ll need to rebuild your Data Structure, but what you have may already work.

There are two paths, one to create objects out from the combined data and another that goes straight to combined CSV.

[Boschung]

Thanks a lot for your support!