https://community.cloudera.com/t5/Support-Questions/merge-too-csv-files-in-nifi/m-p/229267#M191124 <A rel="user" href="https://community.cloudera.com/users/84157/rajatpuchnanda15.html" nodeid="84157">@rajat puchnanda</A><P>Merge a group of flowfile (or) records is possible with MergeContent/MergeRecord processors.</P><P><STRONG>Example:</STRONG></P><P>if flowfile(ff1) having 123 records then ff2 having 345 by using mergecontent/record processors we can merge these flowfiles in to one like 123345.</P><P><STRONG>Merge </STRONG>means combining the group of records/flowfiles(union all) ,if you want to remove duplicates(i.e 3 is duplicate record) from the combined record flowfile content then you can use QueryRecord Processor with row_number window function to eliminate duplicates.</P><P>This scenario is possible with NiFi without using lookup record processors.</P><P>But as you mentioned in one of the answer</P><P><STRONG>Scenario2:</STRONG></P><P>InputFile 1</P><TABLE><TBODY><TR><TD>deptid</TD><TD>firstname</TD><TD>lastname</TD></TR><TR><TD>1</TD><TD>Aman</TD><TD>Sharma</TD></TR><TR><TD>2</TD><TD>Raman</TD><TD>Verma</TD></TR></TBODY></TABLE><P>InputFile 2</P><TABLE><TBODY><TR><TD>deptid</TD><TD>salary</TD><TD>email</TD></TR><TR><TD>1</TD><TD>20000</TD><TD><A href="mailto:abc@gmail.com">abc@gmail.com</A></TD></TR><TR><TD>2</TD><TD>30000</TD><TD><A href="mailto:bgf@gmail.com">bgf@gmail.com</A></TD></TR></TBODY></TABLE><P>OutputFile(By merging file1 and file2):-</P><TABLE><TBODY><TR><TD>deptid</TD><TD>firstname</TD><TD>lastname</TD><TD>salary</TD><TD>email</TD></TR><TR><TD>1</TD><TD>Aman</TD><TD>Sharma</TD><TD>20000</TD><TD><A href="mailto:abc@gmail.com">abc@gmail.com</A></TD></TR><TR><TD>2</TD><TD>Raman</TD><TD>Verma</TD><TD>30000</TD><TD><A href="mailto:bgf@gmail.com">bgf@gmail.com</A></TD></TR></TBODY></TABLE><P>This is not possible with MergeContent/Record but you can try with QueryRecord processor by implementing group and collect as set (or) some sort of sql logic in queryrecord processor to transpose the data into your desired format.This query Would be intensive if you are doing on larger number of records.</P> Thu, 14 Jun 2018 20:00:10 GMT Shu_ashu 2018-06-14T20:00:10Z