(2) Select the book number, library card number and borrowing date of the book in the book borrowing registration form with empty book returning period or book returning period =''.

(3) Select the book number, book return period-book borrowing date as the lending days in the book borrowing registration form with empty book return period or book return period =''

(4) Select ISBN, and count(*) is the number of times to borrow books, and group them according to ISBN from the book borrowing registration form.

(5) select a publishing house, and select sum (price) as the total price from the book list group sorted by publishing house according to the total price desc.