按另一个表的计数选择记录顺序（未在MySQL中检索正确的计数）

Question

在mysql db中，我有两个表book和ratingtable 。

图书表具有三个字段ID,uniqueid,Title

ratingtable具有三个字段Book_ID,userid,rating

我需要一个查询，该查询group by id （书表的） group by id检索记录group by id并按order by count(rating)表的） order by count(rating)检索order by count(rating) 。

我试过这样的查询：

SELECT book.ID,book.Title,COUNT(ratingtable.rating) AS views
FROM book LEFT JOIN ratingtable ON book.ID = ratingtable.book_ID
GROUP BY book.ID
ORDER BY views DESC

但是对于三个值，它将显示错误的计数值。 我不知道会发生什么。

编辑： ratingtable：

书：

在这里，所有的答案[count（rating）]应该为1。 但它显示

帮我解决这个问题。

Answer 1

鉴于您的书号不是唯一的，您得到的结果实际上是正确的。 但是，要获得所需的计数，您可以使用子查询首先将书籍分组，然后进行计数：

SELECT b2.ID, b2.Title,COUNT(ratingtable.rating) AS views
FROM 
    (SELECT b1.id, b1.title FROM Book b1 Group by b1.id, b1.title) b2 
LEFT JOIN ratingtable ON b2.ID = ratingtable.book_ID
GROUP BY b2.ID, b2.Title
ORDER BY views DESC

Answer 2

您需要按书号和书名分组。

SELECT book.ID, book.Title, COUNT(ratingtable.rating) AS views
FROM book LEFT JOIN ratingtable ON book.ID = ratingtable.book_ID
GROUP BY book.ID, book.Title
ORDER BY views DESC

或使用相关子查询进行计数：

select distinct book.ID,
                book.Title,
                (select count(*) from ratingtable
                 where book.ID = ratingtable.book_ID) as views
from book
ORDER BY views DESC