SQL查询未返回最大值

Question

I have written the following query to get the value with the max issue_id. But I get the issue_id 14 for book_id 2. What I want is to get issue_id 16 when book_id is 2. And issue_id 15 when book_id is 3 and so on.

SELECT issue.issue_id AS issue_id, issue.issue_date, issue.student_id, books.availability,
    CASE WHEN NOW() > DATE_ADD(issue.issue_date, INTERVAL 20 DAY)
        THEN 10*DATEDIFF(NOW(), DATE_ADD(issue.issue_date, INTERVAL 20 DAY))
        ELSE 0 END AS fine_amount
        FROM issue
        INNER JOIN books
        ON issue.book_id=books.book_id
        WHERE books.book_id=2 
        HAVING MAX(issue.issue_id)

Answer 1

Use the ORDER BY .. LIMIT 1 to get the highest value

SELECT issue.issue_id AS issue_id, issue.issue_date, issue.student_id, books.availability,
    CASE WHEN NOW() > DATE_ADD(issue.issue_date, INTERVAL 20 DAY)
        THEN 10*DATEDIFF(NOW(), DATE_ADD(issue.issue_date, INTERVAL 20 DAY))
        ELSE 0 END AS fine_amount
        FROM issue
        INNER JOIN books
        ON issue.book_id=books.book_id
        WHERE books.book_id=2 
        ORDER BY issue.issue_id DESC LIMIT 1