Mysql 两个结果集如何相交？

我有两个表

library

和

book

，如这两个块所示

bookid   title  author  publisher 
0        ABC    Abc     abc 
1        DEF    Def     def
2        GHI    Ghi     abc
3        ...    ...     ...

id       discount   price
0         50          8
1         75          6
2         33         10
3         ..         ..

我需要选择每个作者的作品，价格和折扣出版商至少有2个标题，但不超过9。 第一个查询可能是

SELECT title, author, publisher, price, discount FROM library, book

这显然是在返回所有数据。第二个查询可能是

SELECT publisher FROM library GROUP BY publisher 
HAVING COUNT(bookid) > 2 AND COUNT(bookid) < 9

它工作得很好，但在100条记录上速度非常慢，当有1000多条记录时，它根本不工作。如何优化我的查询？

---

提前感谢

这基本上是您的问题：

SELECT l.title, l.author, l.publisher, b.price, b.discount
FROM library l LEFT JOIN
     book b
     ON l.bookid = b.id
WHERE l.publisher IN (SELECT l.publisher
                      FROM library l
                      GROUP BY l.publisher
                      HAVING COUNT(*) < 9 AND COUNT(*) > 3
                     )
ORDER BY l.publisher ASC;

---

那么，我认为这些索引可能会帮助

图书（id）

，

图书馆（出版商，图书id）

，

如果一本书有多个作者呢？非常感谢。它工作得很好。你是我的英雄！：）

Title  Author  Publisher Price   Discount
ABC    Abc     abc       8       ...
GHI    Ghi     abc       10      ...
...    ...     def       11      ...
...    ...     def       11      ...
...    ...     def       9       ...

SELECT l.title, l.author, l.publisher, b.price, b.discount
FROM library l LEFT JOIN
     book b
     ON l.bookid = b.id
WHERE l.publisher IN (SELECT l.publisher
                      FROM library l
                      GROUP BY l.publisher
                      HAVING COUNT(*) < 9 AND COUNT(*) > 3
                     )
ORDER BY l.publisher ASC;

SELECT l.title, l.author, l.publisher, b.price, b.discount
FROM library l LEFT JOIN
     book b
     ON l.bookid = b.id JOIN
     (SELECT l.publisher
      FROM library l
      GROUP BY l.publisher
      HAVING COUNT(*) < 9 AND COUNT(*) > 3
     ) ll
     ON l.publisher = ll.publisher
ORDER BY l.publisher ASC;