userg - the point of second input view on the CSV Parser snap is to allow you to read the file generically. So you would be able to place your table query as the source that defines the input file in the 2nd input view. Your pipeline would look something like this:
Assuming that you use the default config for the Gate snap, and that you read only the target_column_name value from your definition table in the order of input_column_name, then your expression in the Mapper would look like this:
This is simply an Array.join() method to turn the array created by the Gate snap into a single string, with each array element separated by commas.
Note that I've updated the output view of the Mapper to Binary (rather than document) - this allows it to send a Target Path of $content that will be interpreted by the CSV Parser as a binary stream.
Hope this helps!
