Nifi - Merge multiple columns to row

oss a similar problem, could you let me know the best way to handle this scenario. Thanks, Mausam ​

Attribute level interlinked CSV file import

. *Queries:* 1. Is there any out of the box processor that can help implement this? 2. Do I need to use a DB (like mongodb) to persist data for future reference? Thanks in advance. -Mausam