（0，n）和（1，n）基数之间的区别是什么以及如何在给定情况下区分它们。 例如，给定完整性约束，您必须设计er图。我知道首先我应该为每个实体和关系定义基数。
答案 0 :(得分：0)
it depends on your mini-world. for example, in a company, there should be no department without at least one employee. in another company, it is allowed to have a department without any employees related to that deparment.