Join: 4 Joining Columns

Hi @all,

before KNIME I used the vlookup in Excel. I combined more columns and then I made the vlookup.

Now I would like to do that in KNIME.
I´ve join two tables the match needs to be done about 4 columns. But unfortunately it doesn´t work.

KNIME should check if 4 values are equal in both tables and should write the values from column 5 to the left table.

Do you have any idea how to do that?

Thank´s in advance.

BR
Daniela

Could it be that there are spaces before or after the content of any of these columns? Because this could affect the result. Another possibility is that the Join Node is case sensitive while the VLOOKUP in Excel is not, so this could also be the root cause.

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Thank´s :slight_smile: But that´s not the problem.
It creates always an empty data table.

I had same issues by joining multiple string type columns. My workaround was:

  • merge all 4 columns into a temporary column using Column Merger Node in both tables
  • remove all blanks, “-” or other special characters from these temporary columns
  • join both colums according to the temporary column
  • remove the temporary column by column filter or within joiner node

Andreas

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Thank you!
I need to combine then 4 columns. Do I need three Column Merger Nodes and after each of them and Excel Writer Node or is it possible to combine them?

Instead of using 4 Column Mergers you can use one Column Aggregator node.

https://hub.knime.com/knime/nodes/Column_Aggregator*wiIVn14C9BeYBHqr

Yes all of our implementations are case sensitive. So if you have any spaces or changing cases the strings will not match.

Best, Iris

1 Like

Thank´s. Which Aggregation Method should I use?

(There are no spaces or something like this)

I would use Concatenate