英文:
Deciphering the relationship between two entities from the ERD
问题
I want to understand the relationship expressed by the following figure:
The "o" in front of the employee box means zero or one, and the "|" in front of the department means 1 or more. But I am not sure how to express it.
Some things I thought about this could mean:
- A department can have no employees.
- An Employee can work in one or more departments (Not sure if this is true).
- A department can have many employees.
Need some input on the above.
英文:
I want to understand the relationship expressed by the following figure:
The o in front of the employee box means zero or one and the | in front of the department means 1 or more. But I am not sure how to express it.
Some things I thought about this could mean:
-
A department can have no employees
-
An Employee can work in one or more departments (Not sure if this is true)
-
A department can have many employees
Need some input on the above.
答案1
得分: 0
这是一个多对多的关系。 "o" 和 "|" 表示可选或强制元素的信息，更准确地说：
- 一个部门可以有多名员工在其中工作，但也可以没有员工；
- 一个员工必须至少在一个部门工作，并且可以在多个部门工作。
顺便说一下，值得了解更多关于乌鸦脚ERD符号表示法。
英文:
This a many to many relationship. The o and the | tell about optional or mandatory elements, more precisely that:
- a department can have several employees working in it, but could also have none;
- an employee must work in at least one department, and can work in several.
By the way, it's worth discovering more about Crow's foot ERD notation
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