Rule Engine: rewrite only missing data

I have to create a new thread because this is already close:

I don’t know the right syntax in order to execute the rules only in empty cell

Attached you will see 1 of hundreds experiment I made, but no way to find the solution:
If find this text in a cell of colA, then write this text only in empty cell of colB

@ ArjenEX suggest to use AND MISSING #field but i don’t know very wellhow to use.

The problem is the rules rewrite all cells, also some already popolated with a different text

It would be easier for us if you shared some data.

I think the problem in your screenshot is that you’re using TRUE => "NO" instead of TRUE => $77_OMM_ClasseTipeVeicolo ocv novc$. This new rule says that if the previous rule is false, then just return whatever value was originally in column2.

Here’s a simplified example:

Here the example.
How copy the word STAR from ColumnC only in empty cells to ColumnB?

KNIME_project.knwf (8.4 KB)

there is no data in your attached workflow when you reset it before exporting it. In general the rule engine can’t create any formula logic. You might want to check out column expression node for that.

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