MySQL设计表

Question

We have 3 tables.

Instructor
ID (PK, AI)
Name
Surname


Activity
ID (PK, AI)
Name

given_activity
A_ID (FK to Activity ID)
I_ID (FK to Instructor ID)
Slot (PK)

we have designed our tables like this, but we could not satisfy this condition;

"a instructor should not give an activity at the same time"

how could we change our tables?

Answer 1

您的主键可以帮助您在给定的表上创建主键

PRIMARY KEY(a_id,i_id)

Answer 2

The condition:

an instructor should not give an activity at the same time

Is saying that there are no duplicates for instructor/slot in given_activity . You can accomplish this with a unique index/constraint:

create unique index unq_givenactivity_instructor_slot on given_activity(I_ID, slot);

Answer 3

@davejal

making a_id and i_id PK will cause that

"an instructor can not give an activity in different times"

a_id (PK)     i_id (PK)      slot
1             2              10-12
1             2              12-14