Question

This is a SQL view that shows how many books are in the same shelf as the book with the ID ‘2’. Is there a simple way to turn this into a procedure where you can input the book ID, instead of the ID being ‘2’ by default? I haven’t ventured into procedures yet, would this particular procedure involve alot of coding?

    SELECT COUNT(*) FROM books
    WHERE shelf_id = (SELECT shelf_id FROM books WHERE book_id = 2)

The subquery is because the Book table has a shelf ID, but the shelf does not contain book ID’s.

Answer 1

If Oracle, Try something like below:

    PROCEDURE GET_BOOK_COUNT(
        i_book_id            IN  books.book_id%TYPE,
        o_count              OUT NUMBER)
      AS
      BEGIN
            SELECT COUNT(*) INTO o_count  FROM books
            WHERE shelf_id = 
                         (SELECT shelf_id FROM books WHERE book_id = i_book_id );
      END GET_BOOK_COUNT;

But better to make it a function instead of procedure as:

      FUNCTION GET_BOOK_COUNT(
        i_book_id            IN  books.book_id%TYPE)
            RETURN NUMBER
            IS
            l_count Number;
            SELECT COUNT(*) INTO l_count  FROM books
            WHERE shelf_id = 
                         (SELECT shelf_id FROM books WHERE book_id = i_book_id );
            RETURN l_count;
      END GET_BOOK_COUNT;