Concatenate node and empty tables

Hi guys, I’m having serious problems when trying to concatenate several tables in the workflow, that come from another nodes.
The matter is that when of these tables is empty (no result is found) , the concatenade node is not performing, even if the other tables contain data, but no output is released at all after the concatenate node.

How could I manage to make it work and collect data from other non-empty tables?

thank you!!!

Hi @Sgomezba

There is an option in the -Concatenate- node for concatenating tables which do not have the same number of columns “Use union of columns”. If it is selected, it should allow to concatenate tables that do not have the same number of columns or are empty:

Hope this helps.

Saludos cordiales,



The first thing I thought was what @aworker suggested, but I was trying to see what else could it be, since this is the default setting (Use union of columns).

@Sgomezba did you change the settings of the Concatenate node to use intersection?

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Thank you for your replies. Indeed, I have not changed the default option (union of columns). Here it is the node that has empty data, which makes the concatenate not working.


Hello @Sgomezba
Have you checked about the format of the columns that you are trying to concatenate?
I mean: ‘String’ o ‘Number’ against ‘?’


If your first table is an empty table as here, this may be the source of the problem. If order of concatenation is not a problem for you and there is at least one of your tables which is -never- empty, then you could connect the -never empty- table to the first input port to prevent the problem. Otherwise, you could create a fix -fake- first table with just one non empty row which ensures that the concatenation is always valid and then you would just need to remove this fake row eventually. These two solutions should work but may be there is a more elegant solution.


Yes, they are all string columns

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thank you @aworker , it works!

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That is weird. I ruled out that case - first table is empty, because I tested that case on my side, and it still concatenated the other tables as expected…

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