Unable to implement join properly - php

Question

I am trying to figure out
(book_id, branch_id, total_copies, number_available)
Here is the schema:
Here is as far I have gone:
SELECT
TITLE,
A.BOOK_ID,
A.BRANCH_NAME,
A.BRANCH_ID,
NO_OF_COPIES,
COUNT(BOOK_LOANS.BOOK_ID) AS NUM_OUT,
NO_OF_COPIES - COUNT(BOOK_LOANS.BOOK_ID) AS NUM_AVAIL,
AUTHOR_NAME
FROM
(SELECT
TITLE,
BOOK.BOOK_ID,
BOOK_COPIES.BRANCH_ID,
BRANCH_NAME,
NO_OF_COPIES,
BOOK_AUTHORS.AUTHOR_NAME
FROM
BOOK,
BOOK_COPIES,
LIBRARY_BRANCH,
BOOK_AUTHORS
WHERE
BOOK_COPIES.BOOK_ID=BOOK.BOOK_ID
AND BOOK_AUTHORS.BOOK_ID = BOOK.BOOK_ID
AND (
BOOK.TITLE LIKE :title
OR BOOK.BOOK_ID = :book_id
OR BOOK_AUTHORS.AUTHOR_NAME LIKE :author_name
)
AND BOOK_COPIES.BRANCH_ID=LIBRARY_BRANCH.BRANCH_ID) AS A
LEFT OUTER JOIN
BOOK_LOANS
ON A.BOOK_ID=BOOK_LOANS.BOOK_ID
AND A.BRANCH_ID=BOOK_LOANS.BRANCH_ID
GROUP BY
A.BOOK_ID,
A.BRANCH_ID
But the problem I am encountering is, since BOOK_AUTHORS table has multiple authors for a single book. So I am able to understand that joining only on book_id of BOOK and BOOK_AUTHORS while I should be able to completely using the both book_id and author_name.
So its returning the count 2 times for a single entry in book_loans.
e.g. If a book with book_id lets say 1234 is checked out once, and it has total copies of 2, so it should return remaining copies as 1. But its returning 0.
Please help me understand how to fix this.
Note: I am using php prepare statement.

Answer 1

I didn't pay attention on you query (too complicated to me),
COUNT(DISTINCT BOOK_LOANS.BOOK_ID) rather than COUNT(BOOK_LOANS.BOOK_ID). If you query works well except its count, DISTINCT is helpful.
performance matters. I guess inline view is too complicate. I wonder if changed like this
SELECT
DISTINCT BOOK.BOOK_ID
FROM
BOOK INNER JOIN BOOK_AUTHORS USING(BOOK_ID)
WHERE
BOOK.TITLE LIKE :title
OR BOOK.BOOK_ID = :book_id
OR BOOK_AUTHORS.AUTHOR_NAME LIKE :author_name
Then final query looks like this
SELECT
TITLE,
BOOK.BOOK_ID,
LIBRARY_BRANCH.BRANCH_NAME,
LIBRARY_BRANCH.BRANCH_ID,
BOOK_COPIES.NO_OF_COPIES,
COUNT(distinct BOOK_LOANS.BOOK_ID) AS NUM_OUT,
BOOK_COPIES.NO_OF_COPIES - COUNT(distinct BOOK_LOANS.BOOK_ID) AS NUM_AVAIL,
AUTHOR_NAME
FROM
(
SELECT
DISTINCT BOOK.BOOK_ID
FROM
BOOK,
BOOK_AUTHORS
WHERE
BOOK.TITLE LIKE :title
OR BOOK.BOOK_ID = :book_id
OR BOOK_AUTHORS.AUTHOR_NAME LIKE :author_name
) AS A
INNER JOIN BOOK USING(BOOK_ID)
INNER JOIN BOOK_AUTHORS USING (BOOK_ID)
INNER JOIN BOOK_COPIES USING(BOOK_ID)
INNER JOIN LIBRARY_BRANCH USING(BRANCH_ID)
LEFT OUTER JOIN
BOOK_LOANS
ON BOOK.BOOK_ID=BOOK_LOANS.BOOK_ID
AND LIBRARY_BRANCH.BRANCH_ID=BOOK_LOANS.BRANCH_ID
GROUP BY
BOOK.BOOK_ID,
LIBRARY_BRANCH.BRANCH_ID,
LIBRARY_BRANCH.BRANCH_NAME,
BOOK_COPIES.NO_OF_COPIES,
AUTHOR_NAME