MYSQL count() error

Question

SELECT Author, count(Heading) AS "No. of books" FROM BOOKS GROUP BY Author;

当前显示每位作者写了多少本书。

如何使代码仅返回写了 2 本书的作者？

Answer 1

您可以使用 for 过滤聚合函数的结果

SELECT Author, count(Heading) AS "No. of books" 
FROM BOOKS 
GROUP BY Author
HAVING count(Heading)  = 2 ;

Answer 2

试试这个!!

SELECT Author, count(Heading) AS "No. of books"  
FROM BOOKS  
HAVING count(Heading)  = 2  
GROUP BY Author;