如何建模这种数据库关系？ （sybase powerdesigner）

Question

I'm doing a conceptual model in Sybase PowerDesigner.
The restriction is following:
One doctor can work in only one office at a time during his working time (shift).

I guess Doctor - Office relationship should be many-many, but what about 
time restriction ("during his working time")?
Should it be a new table SHIFT?

So I guess I should have four tables (DOCTOR, OFFICE, SHIFT and OFFICE SCHEDULE).
OFFICE SCHEDULE should be a table connecting all 3 other entities 
and should have composite primary key (id_doctor, id_office, id_shift)?

Answer 1

该密钥（id_doctor，id_office，id_shift）将允许医生在一个班次的许多办公室工作。尝试一张关于医生和轮班的办公室的钥匙 - 办公室是一个依赖的领域。然而，这将允许办公室在轮班中拥有多名医生，我不确定是否允许这样做。

Answer 2

我会将您的主键更改为仅包括办公室和班次，但也会在医生处添加一个独立的约束并一起转移。

Answer 3

OFFICE SCHEDULE的主键应该是（id_office，id_shift）。 id_doctor应该在表中，但不是主键的一部分。这将强制执行给予办公室的规则，并且在该办公室中最多只能有一名医生。

当然，除了构成主键的两个外键之外，所有这三个都是外键。