Problem with Join

KNIME Analytics Platform
1

Hi everyone!

I am fairly new to KNIME, trying to do some simpler stuff...Nevertheless I have a problem with the JOINER node:

I have two .csv files with data (1 - main file, 2 - additional information I want to add to the first file in a new column). The two files share one column with the same kind of information that I would like to match (kind of like VLOOKUP in Excel...). The problem is the following: After I use the JOINER node to add the new column, the row number of the main file is incorrect (it should stay the same). I used the Left Outer Join and after the execution I have more rows than in the original file, it should be the same amount of rows though since I just want to add a new column with the additional information. Does anyone know what the problem here could be? Additional settings, see attached.

Thank you very much!!

 

 

2

Hi,

A LEFT OUTER JOIN returns one row from the LEFT table for each match in the RIGHT table. If you happen to have multiple matches in the RIGHT table (e.g. it contains duplicates), you end up with more rows in your result than in the original LEFT table.

In your case I would use a Cell Replacer node (dictionary lookup) instead. Use the second (RIGHT) table as dictionary and Append the results to the first table. This guarantees the number or rows in the first (LEFT) table stay the same.

Cheers,
Marco.

3

Hi Marco!

Thank you very much for your quick answer - I have one duplicate and that results in quite a large difference within the output file...I tried to find another way to do this before but did not see the Cell Replacer node. It is working fine now, thanks a lot!!!