Question

Let’s say I have two databases: one contains a list of books which are in my possession, the other contains a list of all allowed_books which are allowed by the government to be in my possession (okay, perhaps a bad example, but you’ll get the idea soon). The allowed_books database is constant and consistent. If a Book in my books database isn’t also in the allowed_books database, I need to delete it from books.

What is the best way to do this?

Is there a Rails/Sqlite function/method that will compare two databases and remove extraneous entries? Or do I have to do this somewhat manually?

I was thinking that before I actually create a new Book, I’ll run something like AllowedBook.find_by_name(book_name) on it first. If it returns nil, then I won’t add it in the first place. Or if, as stated above, Rails/Sqlite has some default way to check for inconsistencies between databases, is this a better option?

I’m fairly certain I can do it manually using find_by_name, but is this the best option?

Ruby 1.9.3, Rails 3.2.6, SQLite3 3.6.20.

Thanks!

Answer 1

I’m assuming that you mean “two tables”, not “two databases”. There is no way to do what you suggest in either Rails or Sqlite. You have to do it manually.