How to use two sqlite database within single application and how to use join operation with them?

I have read many questions & answers related to my question but I am not getting a proper way for doing this.

Condtion:

I have three tables in SQLite database. I want to update the data of two (TBL_NAMES,TBL_CATEGORY) tables without losing the data of third table (TBL_FEVORITE) whenever my application get an update.

My application would work offline, so the new records will be provided to me with SQLite database.

What I did?

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  I did put the updated database in asset folder and tried to access from my `DatabaseHelper' class but, it is not accessible.

  
  


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  I tried to create two different database (one for TBL_NAMES & TBL_CATEGORY and second one for TBL_FEVORITE) but did not succeeded.

  
  

Please suggest how can I do this? How can I keep two database open if I would use two databases or how can I update the database from updated database except one table.