Question

Goodevening，溢出者！

我正在尝试显示已签出多个book_copy的教师客户的CID，以及check_copies签出的数量。我必须使用HAVING语句。教师是CUSTOMER表属性“CATEGORY”下的三种类型之一。我尝试了一些不同的东西，但现在我就是这样：

Select OUT_TO_CID "CID", count(COPY_NUM) "Books checked out" from BOOK_COPY
group by OUT_TO_CID having count(COPY_NUM) > 1;

这段代码有效，并且允许我以正确的方式向所有客户展示多个book_copy签出 - 不幸的是，我应该只为教职员工展示它。但是我如何从这里到达那里？嵌套子查询是解决方案吗？

好的，所以我现在尝试使用嵌套的子查询，但我很确定我做错了......：D我现在在从子开始的子查询行中出现错误。

Select OUT_TO_CID "CID",
count(COPY_NUM) "Books checked out"
from BOOK_COPY
group by OUT_TO_CID
having count(COPY_NUM) > 1
in (select CID from CUSTOMER where CATEGORY = 'Faculty')
;

这些是有问题的表格：

create table BOOK_COPY
(Copy_Num number(5),
Bookid  number(5),
out_to_CID number(6),
Date_Out date,
Date_Due date,
Held_Until date,
held_for_CID number(6),
CONSTRAINT PKCOPY PRIMARY KEY (Copy_Num,Bookid),
CONSTRAINT FKCID FOREIGN KEY (out_to_CID) references CUSTOMER (CID),
CONSTRAINT FKHeld FOREIGN KEY (held_for_CID) references CUSTOMER (CID),
CONSTRAINT FKBookid FOREIGN KEY (Bookid) references BOOK (Bookid));

create table CUSTOMER
(CID number(6),
First_Name varchar2(12),
Last_Name varchar2(12),
Category varchar2(7),
Balance_Due number(4,2),
SponsorID number(6),
CONSTRAINT pkCID PRIMARY KEY (CID),
CONSTRAINT fkCUSTOMER foreign key (sponsorID) references customer);

如果我的帖子有些违反规定，请告诉我。并感谢阅读它到最后; - ）

Answer 1

您已经到了一半，因为您了解必须加入2个表才能按类别过滤。因此，这就是我们要做的：

Select b.OUT_TO_CID "CID",
count(b.COPY_NUM) "Books checked out"
from BOOK_COPY b
inner join CUSTOMER c on b.out_to_cid = c.cid
where c.category = 'Faculty'
group by b.OUT_TO_CID
having count(b.COPY_NUM) > 1

Oracle SQLPlus列出值为＆＃39;有＆＃39;来自多个表

1 个答案: