How do I loop through same ID in many rows?


I have one simple database where the same number appears in two columns and I would like to get the full chain.

Database example (also .xlsx attached):


Cod1 Cod2
1 2
2 3
3 4
5 6
6 7
8 9
10 11
11 12


Col1 Col2 Col3 Col4
1 2 3 4
2 3 4
3 4
5 6 7
6 7
8 9
10 11 12
11 12

I appreciate the assistance.
Example.xlsx (9.9 KB)

I could think of using a lag node for column 1 and check if col2 = lag col 1.
Maybe someone comes up with a better idea

Or a “negative lag” to look down Cod2 in order to test if it falls sequentially so that it can be moved to a new column.

This negative lag style approach may also now be possible just using the Column Expression node with the recent addition of multi-row support, but I haven’t had time to delve into it yet…

I guess you could also loop through rows in one Cod1, append it to a “transformed” Cod2, test for when the columns fail to fall in sequential order, then delete the remaining columns, then concatenate your row results into a table at loop end. Slower processing, but it should work as an alternate option.

Hi @jonatasflausino and welcome to the Knime Community.

Is it similar to this?


Hello, @bruno29a.

This worked like a charm, thanks a lot.
I just needed to split later the cell into columns.

Many thanks for your support!

1 Like

I wasn’t thinking about it along the lines of Parent / Child relationship without the context in the sample data. Great approach @bruno29a! I am going to incorporate this into projects as well!


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