It looks like comment - it informs database how process query
SELECT /*+ LEADING(e2 e1) USE_NL(e1) INDEX(e1 emp_emp_id_pk)
LEADING - about join order
USE_NL - use nested loops algorithm for ....
INDEX - use index ......
USE_MERGE - merge join algorithm
FULL(j) - full table scan of j
I don't see anything on my end where hints is supported. If it can be deployed to function automatically at the backend DB level then maybe it's still doable, but that said it's not going to reflect back in Campaign so if Hints changes the query and breaks something the only way that you'll be able to troubleshoot would be to review the executed SQL from the DB side directly and making changes on the application side may not have any impact if Oracle is making it's own changes on the fly.
So I'd advise against using Hints personally.