SQL 如何根据来自多行的值 select 行

Question

嗨，我运行遇到了与下表有关的问题

       CREATE TABLE BOOKS ( 
          Title varchar(255),
          Year INT,
          Type ENUM("Horror", "Fantasy"),
          Pages INT,
          PRIMARY KEY (Title, Year)
        );
        
        CREATE TABLE AUTHORS(
          Title varchar(255), 
          Year INT, 
          PlaceOfBirth varchar(255), 
          AuthorName varchar(255),
          PRIMARY KEY (Title, Year, PlaceOfBirth ),
          FOREIGN KEY (Title, Year) REFERENCES BOOKS(Title, Year)
        );

现在想查询所有只有40页以上恐怖书的作者

SELECT a.AuthorName, b.Pages FROM AUTHORS a INNER JOIN BOOKS b ON a.Title=b.Title AND a.Year=b.Year
WHERE  b.Type="Horror" AND b.Pages > 40

现在的问题是，我得到那些写过超过 40 页的恐怖书的作者，但他们也可能有不到 40 页的恐怖书。我想要那些只写 40 页或更长的恐怖书的作者。

Answer 1

如果您想要至少写过一本恐怖书并且所有此类书都超过 40 页的作者姓名，您可以使用 group by 和 having:

select a.authorname
from authors a 
inner join books b on a.title = b.title and a.year = b.year
where b.type = 'Horror' 
group by a.authorname
having min(b.pages) > 40

SQL 如何根据来自多行的值 select 行

SQL How to select rows based on values from multiple rows

sql

select

inner-join

aggregate-functions

having-clause