MySQL查詢圖書館管理系統

Question

我有以下表

成員（memberNo，姓名，年齡），

書（ISBN，書名，作者，出版者，出版年，類別）

借（memberNo，ISBN，日期）

和我期待的答案或線索以下查詢

查找成員的瓦時的名字o不止一次借過同一本書。我一直在使用下列但它給我就列名「name」

SELECT member.name 
    FROM member 
    WHERE member.memberNo IN (SELECT borrowed.member_memberNo 
    FROM borrowed 
    WHERE borrowed.book_isbn IN(
    SELECT COUNT(borrowed.book_isbn) as 'countNo' 
    FROM borrowed 
    WHERE 'countNo' >1)); 

非常感謝

！

Answer 1

您可以使用GROUP BY和COUNT來查找成員借用每本書的次數。

SELECT memberNo, isbn, COUNT(*) AS borrow_times 
FROM borrowed 
GROUP BY memberNo, isbn 

然後檢查borrow_times > 1找到誰借的同一本書不止一次的：

：

HAVING borrow_times > 1 

將這個變成一個子查詢，以便您可以用member表加入吧

SELECT DISTINCT m.name 
FROM member AS m 
JOIN (
    SELECT memberNo, isbn, COUNT(*) AS borrow_times 
    FROM borrowed 
    GROUP BY memberNo, isbn 
    HAVING borrow_times > 1 
) AS b ON m.memberNo = b.memberNo