Hello @Jeevi Danda ,
Thanks for the question and using MS Q&A platform.
As of today, the ADF copy mergeFiles
behavior doesn't have control over the order of files to be merged and also the order of rows to be merged. It considers randomly.
If you have feedback regarding this, I recommend submitting a feature request for the same in ADF IDEAS forum here: https://feedback.azure.com/d365community/forum/1219ec2d-6c26-ec11-b6e6-000d3a4f032c
All the feedback shared in this forum are actively monitored and reviewed by respective product owners. Please do share the feedback link once it is posted so that I shall up-vote it and also will pass the feedback to respective product owners.
Hope this info helps.