Count子句中的函数不起作用

Question

    SELECT Book_Title, Publisher_Name, Book_Type, Author_Last, Author_First

    FROM Book,  Author, Publisher, Wrote

    WHERE Author.Author_Num=Wrote.Author_Num

    AND Wrote.Book_Code=Book.Book_Code

    AND Book.Publisher_Code=Publisher.Publisher_Code

    GROUP BY Wrote.Book_Code, Book_Title,  Book_Type, Publisher_Name, Author_Last, Author_First 

    HAVING COUNT (Wrote.Book_Code)=2;

目标：列出包含两位作者的每本书的标题，出版商名称，类型和作者姓名。

当我运行此查询时，我得到空行。有人帮忙为什么会这样吗？

Answer 1

SELECT Book_Title, Publisher_Name, Book_Type, Author_Last, Author_First

FROM Book,  Author, Publisher, Wrote

WHERE Author.Author_Num=Wrote.Author_Num

AND Wrote.Book_Code=Book.Book_Code

AND Book.Publisher_Code=Publisher.Publisher_Code

GROUP BY Wrote.Book_Code

HAVING COUNT (Wrote.Book_Code)=2;