MYSQL count（）error

Question

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

當前顯示每個作者寫了多少本書。

我該如何才能讓代碼只返回已經寫完2本書的作者？

Answer 1

可以使用具有過濾結果爲聚合函數

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

Answer 2

試試這個！

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