Question

I’m making a webpage for a library and I need to make a list that shows all the books which are not rented within the past year.

At the moment I have a Query that filters on the Rent table, where all the records are of rented books. But can be rented multiple times so a book can show up multiple times in the table. The problem is, when a book isn’t rented to a person for more then a year, but the same book is rented to another person within the past year, it shows still that book because it saw one record fullfilling the conditions. But I need to know which book isn’t rented at all in the past year. Can anyone help me with that?

I changed the real query to an easier to understand query (language difference), so don’t check on bad spelling or simple syntax problems.

My query a.t.m.:

SELECT
  Book.BookID,
  Book.BoekTitle, 
  Writer.WriterName 
FROM (
    (Book INNER JOIN BookWriter ON Book.BookID=BookWriter.BookID) 
    INNER JOIN Writer ON BookWriter.WriterID=Writer.WriterID
  )
  INNER JOIN BookRenting ON Book.BookID=BookRenting.BookID
WHERE
  BookRenting.RentDate < DATEADD('yyyy', -1, NOW());

I use an MS Access database!

Thanks in advance for helping me!

Answer 1

First, you probably need to take care of the condition where the book has never been rented. This requires an outer join.

This should get you what you want:

select b.BookID, b.BookTitle, w.WriterName
from book b left outer join
     (select BookId, max(RentDate) as MaxRentDate
      from BookRenting br
      group by BookId
     ) br
     on b.BookId = br.BookId left outer join
     BookWriter bw
     on b.BookId = bw.BookId left outer join
     Writer w
     on bw.WriterId = w.WriterId
where br.MaxRentDate < DATEADD('yyyy', -1, NOW());

And, I meant to add that books can have multiple writers. You will still get duplicates in the output.