Question

我有下表

成员（memberNo，姓名，年龄），

书（isbn，title，author，publisher，year，category）

借（memberNo，isbn，date）

我正在寻找以下查询的答案或线索

查找多次借用同一本书的会员姓名。

我一直在使用以下内容，但它只给我一个名称'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));

非常感谢！

Answer 1

您可以使用GROUP BY和COUNT查找会员借阅每本书的次数。

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

然后检查borrow_times > 1是否找到多次借用同一本书的人：

HAVING borrow_times > 1

将其放入子查询中，以便可以将其与member表连接：

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

库管理系统的mysql查询

1 个答案: