Is there a tutorial on how i can use plugins to retrieve information from external database

The use case i am trying to implement is :-

1. There is an external oracle database containing archived documents, which Joget users might want to upload them during a workflow.
2. this external database is not part of the Joget workflow database.
3. what i need to do is during certain workflow activity to allow the users to retrieve all the archived documents from the database that have the "creator_name" column  = the login user. The sql statement should be something similar to "select data from document where creator_name = #requestor.username#."
   

But me question is how i can implement the above use case and where i should write the sql to retrieve the related documents?

Best Regards