Question

我有CAMPUS_IDs（NY1，PA1，VA1）和CLASS_IDs（大约10个班级）所以我必须创建一个包含Campus_id和Class_id列的表，并指定在哪个校区中教授课程。问题是所有校区都会教授一些课程，其中一些课程只在一个校区内授课。如何设计那张桌子？我试图创建下表，但它很乱：

_____________________
| class_id  |campus_id
---------------------
| math101   | NY1    |
---------------------
| pyt218    | PA1    |
---------------------
| C767      | VA1    | 
---------------------
| pyt218    | PA1    |
_____________________

和带有class_id的campus_id是另一个表的外键。

Answer 1

所以你想列出所有课程的校园？对于像

这样的输出

class_id | campus_id
math101  | NY1, PA1
pyt218   | PA1, VA1, NY1
...

您可以使用Oracle 10g中提供的wm_concat函数：

with d as (
  select 'NY1' as campus_id, 'math101' as class_id from dual union all 
  select 'PA1' as campus_id, 'math101' as class_id from dual union all 
  select 'VA1' as campus_id, 'pyt218' as class_id from dual union all 
  select 'PA1' as campus_id, 'pyt218' as class_id from dual union all 
  select 'PA1' as campus_id, 'class3' as class_id from dual union all 
  select 'VA1' as campus_id, 'class3' as class_id from dual union all 
  select 'VA1' as campus_id, 'math101' as class_id from dual union all 
  select 'NY1' as campus_id, 'class3' as class_id from dual
)
select class_id, wm_concat(campus_Id)
From d
group by class_id

在Oracle 11.2中，有一个新功能“listagg”可用于生成相同的结果：

with d as (
  select 'NY1' as campus_id, 'math101' as class_id from dual union all 
  ...
)
select class_id, listagg(campus_id, ',') within group (order by campus_id)
From d
group by class_id

找到校园里的课程

1 个答案: