Suppose you are creating a database for a library management system. Explain how you would create a table for the "books" entity and insert some sample data, and then alter the table to add a new column for the "authorID" attribute and update “authorID” with some data. Finally, write a SQL query to retrieve all the books that were published after the year 2000.
Note that this book schema has several columns, including "book_id" as the primary key, "title", "authorN", "publisher", "publication_year", "isbn", "language", and "num_pages". It also includes "available" column that is set to "true" by default and can be used to track the availability of the book.