Dear all, I have to check a table if a column exists. If yes (column is already existing): column values should be set to null if no(column is not existing): column should be added. in pseudo code: if exists (column"test") then all column(“test”)=null else add column(test) In forum I found an node if column exists from column, but I can’t find it. Is there a smart way to realize? Thanks for help! BR, Heinz

I think (hope!) it was resolved here… :wink: [image] If column exists node not available KNIME Analytics Platform Thank you very much for detailed explanation. Please find below my comment: I terminated (exit) temporary ZScaler that was running on my machine (maybe you have to contact your IT Admin to be allowed to do this). After this was done, there was no problem to insert the requested component into my workflow by using drag and drop. Then I activated ZScaler again. BR, Heinz

Hi @Heinz I have an “If Column Exists” component on the hub which maybe you’ve seen on the forum? Just type in the column name you want to test and use it like a regular If node [image] [image] (edit: corrected the images to note use of toNull() to create missing values. [image] IF Column Exists – takbb Provides a switched branch. If the named column exists, the upper branch is active. If the named column doesn't exist, the lower branch is active @takbb Brian …

Hi Heinz, There is a „extract table spec“ node. It delivers the column names. Based on this you can add a row filter and a construct a „if-else“ loop

Yes, internally my above component does uses “extract table spec”. There is also this clever alternative demo workflow from @s.roughley which uses the Vernalis nodes to solve this problem, so that’s another option too :wink: [image] If Column Exists – s.roughley Solutions for data science: find workflows, nodes and components, and collaborate in spaces. It featured on the following forum thread [image] Editing java Snippet node to check if column exist or create it KNIME Analytics Platform With the new Array-type variables which I think have happened since this original question, along with the new-ish @Vernalis Configurable IF/CASE... nodes, it is possible to do this with no scripting requirements: [image] The Extract Column Header / GroupBy / Table Row to Variable sequence puts the column names into an array variable, and then the Configurable IF/CASE Switch (Flow Variable Value) node can test various options for members of the array, including the selected Any Equals option f…

@Heinz using code there is also this solution [image] Editing java Snippet node to check if column exist or create it KNIME Analytics Platform @tommasopalomba a pretty basic code with columnExists : out_colExists = columnExists(v_var_column_to_check) ? 1 : 0; [image] will give you a flow variable that you can then further use to steer a switch or something. [image]

That is the node I had in mind. But I can’t find it searching in the nodes… I am using latest Knime with all updates. When tyring to insert the node using drag and drop from your workflow I got the message: ERROR CreateMetaNodeTemplateCommand Metanode loading failed with CoreException: The entity is not backed by an input stream, entity class is : java.io.InputStream Any hint? Thx for help! BR, Heinz

Hope you’ve found what you were looking for by now. [image] Heinz: But I can’t find it searching in the nodes…

if column exists

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mlauber71 January 9, 2025, 10:46pm 5

@Heinz using code there is also this solution