ER图中2个实体之间的2关系 [英] 2 relationships between 2 entities in ER diagram

问题描述

- 部门雇用员工

$ b $一个员工是特殊，具有更多的属性

- 员工（特殊和非特殊）中的一些是经理

- 经理管理部门

所以，为了表达我，我有：

 部门------（雇佣）-------员工-----< ---- ----特价
 | | 
 | -----------（管理）---------- 
  

从我的理解，我不能在2个实体之间有2个关系。如何处理这种情况？

解决方案

没有理由你不能在同一个两个实体之间有多个关系你的理解在这方面是错误的。

当然，你必须确定这些关系捕获不同的信息，而且你没有错误地说单一关系的两个方面是两个不同的关系。你的例子似乎是两个实体之间有两个关系的好选择。

I'm trying to draw an ER diagram describing the following:

-"Department" employs "Employees"

-Some "Employees" are "Special" and have more attributes

-Some of the "Employees" ("Special" and non special) are "Managers"

-"Managers" manage "Departments"

So, to convey this I have:

Department ------(employs)------- Employee-----<--------Special
      |                             |
      |-----------(manages)----------

From my understanding, I cannot have 2 relationships between 2 entities. How do I deal with this situation then?

解决方案

There is no reason you can't have multiple relationships between the same two entities, your understanding is wrong in this respect.

You have to be certain, of course, that the relationships capture different information and that you haven't, say, mistaken the two aspects of a single relationship as two different relationships. Your example seems to be a good candidate for having two relationships between the two entities.

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