Concatenate a field based on grouping of another field

[camjam980]

I have a report I'm trying to create that would have a list of expense reports and the attendees that were present. I'm trying to see if I can concatenate the attendees into a string delimited by comments based on the report ID to use as a field for a column of the report.

Are there any functions which can concatenate a field of values separated by a character? Similar to java's String.join(',', array);