第一个查询涉及与特定主题相关的书籍和作者列表，并生成正确的结果：

SELECT BOOK_NUM,
BOOK_TITLE,
BOOK_SUBJECT,
AU_LNAME
FROM BOOK
JOIN WRITES USING (BOOK_NUM)
JOIN AUTHOR USING (AU_ID)
WHERE BOOK_SUBJECT = 'CLOUD'
ORDER BY BOOK_TITLE;

第二个扩展了主题，也产生了正确的结果：

SELECT BOOK_NUM,
BOOK_TITLE,
BOOK_SUBJECT,
AU_FNAME,
AU_LNAME,
Count(BOOK_TITLE) AS `NUM BOOKS BY AUTHOR`
FROM BOOK
JOIN WRITES USING (BOOK_NUM)
JOIN AUTHOR USING (AU_ID)
GROUP BY BOOK_NUM, AU_ID
ORDER BY `NUM BOOKS BY AUTHOR`,
AU_LNAME;

当我将两者结合起来时，会在book\u subject='cloud'处产生语法错误：

SELECT BOOK_NUM,
BOOK_TITLE,
BOOK_SUBJECT,
AU_FNAME,
AU_LNAME,
Count(BOOK_TITLE) AS `NUM BOOKS BY AUTHOR`
FROM BOOK
JOIN WRITES USING (BOOK_NUM)
JOIN AUTHOR USING (AU_ID)
GROUP BY BOOK_NUM, AU_ID
WHERE BOOK_SUBJECT = 'CLOUD'
ORDER BY `NUM BOOKS BY AUTHOR`, 
AU_LNAME,
BOOK_TITLE;

不管我把它放在哪里，我都会得到同样的错误，如果我删除它，代码就会运行。我需要怎么做才能解决这个问题？我需要把这个where子句包括在内。事先谢谢你帮我。