2 查询单独运行良好但组合产生语法错误

Question

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;

第二个扩展了主题并产生了正确的结果：

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，它会在 WHERE BOOK_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;

无论我把它放在哪里，我都会得到同样的错误，如果我删除它，代码就会运行。我需要做什么来解决这个问题？我需要包含这个 where 子句。预先感谢您帮助我。

Answer 1

不确定 SQL 您使用的是什么。尝试将 WHERE 子句移动到 GROUP BY 之上。

Answer 2

好问题。尝试参考一些关于表达式顺序的文档...

尝试以下代码，我们在其中适当地移动了 WHERE 语句。

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)

WHERE BOOK_SUBJECT = 'CLOUD'

GROUP BY BOOK_NUM, AU_ID

ORDER BY `NUM BOOKS BY AUTHOR`, 
AU_LNAME,
BOOK_TITLE;

2 查询单独运行良好但组合产生语法错误

2 Queries work well separately but combined produce a syntax error

mysql

where