KNIME basic idea


First of all I would like to apologize for not very smart questions, but I can not find answers anywhere.

I am quite familiar with ETL Pentaho and mainly I am using it for some text parsing, joining, transforming etc.

I can not say I am real professional, but I am not bad in it. Due to some reasons I need to start with KNIME as well and I feel really desperate. I think I didn’t get the KNIME idea behind. In Pentaho for each step or node I can make double click and setup everything I need, but it seems like in KNIME it doesn’t work in this way. Especially some conditions like if or case etc. how these nodes are controlled. Everything in KNIME is controlled by variables or how? In Pentaho I setup for each step everything directly, but here I am completely out.

In Pentaho is these steps so easy, but here I can not get KNIME idea. Such simple condition like ïf this filed = 0 go here all other values here” I feel like an idiot. Can someone clarify it for me?

Thank you so much.


Hi there @sm0lda,

welcome to KNIME Community Forum and let’s see if I can help you although not Pentaho familiar.

So KNIME is also double click, setup/configure and run - hopefully successfully :smiley: Regarding (flow) variables, the answer is no, everything in KNIME is not controlled by flow variables. If so that would be really bad. But coming to Switch nodes (IF Switch and CASE Switch Data (Start) for example) one should use flow variables to dynamically control flow. Good thing KNIME has are bunch of workflow examples which you can download and run (again hopefully successfully :smiley:) and get familiar with a certain node or functionality. See here for basic switching examples. KNIME also has a lot of training materials which you can check. Hope this helps!

If you will still need help with flow variables and switches I can make you an examples based on your actual case if you are willing to share it :wink:

Happy KNIMEing!



I assume that

node may help in your case.

Hello Ivan,

thank you for your quick reply.

Can you just give me some hint how to do some normalization like this? Only show which nodes i have to use for it.

input streams are columns number and string B/KiB/MiB/GiB

based on B/KiB/MiB/GiB i have to chose correct data flow to go into

Uplodd Volume
10 B
10 KiB
10 MiB
10 GiB

output i want to make some kind of normalization to KiB only, to be able make some comparison
Upload Volume Upload [KiB]
10 B =10/1024 = 0.0098
10 KiB =10 no activity = 10
10 MiB =101024 = 10 240
10 GiB =10
1024*1024 = 10 485 760

standardisation_knime_table standardisation_pentaho

Thank you my friend so much!


For this purpose

will do the job. If statement corresponds to Java syntax
if () {} else {}


Hi there @sm0lda,

as @izaychik63 mentioned you can use Column Expressions node which is based on JavaScript syntax and write Switch statement for example.

Another thing you can do is use Rule Engine to output multiplayer in new column depending on Uploaded Type and then in Math Formula multiply two columns. Here is example:

2020_02_07_Condition_Multiply.knwf (12.8 KB)

Take a look and if any questions feel free to ask.



A post was split to a new topic: Number cunt in a cell

Yeah I would also go with the Rule Engine for multiplier and Math formula. The column expressions for me is too slow for use with lots of data.

Hello @ipazin it works perfectly. I used Rule engine + Math formukla. Thanks a lot!

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