Question about 'valid UNSW course id'

[Shaoyang]

Hi there,

The 'valid UNSW course id' mentioned in Q1 means as long as an id exists in 'Courses' table it is valid, is my understanding correct?

Thanks,

Shaoyang

[Wei Li]

if not exists course_enrolments.course = course_id, not found

[Rui Liang]

Hi Wei,

I am also confused about the invalid "course_id", according to what Kai post earlier, we should consider the function input "course_id" in the "course" table (compare with "course.id"), and if no student enrols in this course (which suggests that "course_id" will not exist in "course_enrolments" table), we should output the number of all the rooms even with room.capacity is null, but not raise an exception. If  "course_id" does not match any "course.id" in "course" table, we should raise "INVALID COURSEID".

However, according to your post, it suggests that we should consider the function input "course_id" in the "course_enrolments" table and compare with "course_enrolment.course", if the "course_id" does not match any "course_enrolment.course", we should raise an exception (which means if no student enrol in this course, then we should raise an exception). But according to Kai, we shouldn't raise an exception if "course_id" exist in "course" table event thought it does not exist in "course_enrolments" table.

So when the function input "course_id" exists in "course" table but not in "course_enrolments" table, which one should I follow?

The following is a screenshot of Kai's post. (https://groups.google.com/forum/#!category-topic/comp9311-project-qa/project2-q1/3Jm0Fb6-2VI)

Regards,

Rui

在 2018年5月11日星期五 UTC+10上午9:32:29，Wei Li写道：

[Shaoyang]

Thank you Rui, maybe both Kai and Wei are correct however which suggestion we should follow?

在 2018年5月12日星期六 UTC+10上午1:45:09，Rui Liang写道：

[Shaoyang]

Thank you Wei, you are correct since if no students enrolled in a specific course_id, it makes no sense to return all rooms. However which strategy we should follow? Thank you.

在 2018年5月11日星期五 UTC+10上午9:32:29，Wei Li写道：

if not exists course_enrolments.course = course_id, not found

[Kai Wang]

if not exists course_enrolments.course = course_id, raise exception.

Kai

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[Kai Wang]

Hi Rui,

Both of these two solutions are all accepted.

Kai

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[Rui Liang]

Hi Kai,

Got it, thanks for your help.

Rui

在 2018年5月12日星期六 UTC+10下午1:41:12，Kai Wang写道：

[Teng Long]

Hi Kai,

Just an additional guess, can we assume that every course_id from the course table will have a corresponding record from the course_enrollment table?

Regards,

Teng

在 2018年5月12日星期六 UTC+10下午1:41:12，Kai Wang写道：

Hi Rui,

[Kai Wang]

If a course_id from the course table doesn't have a corresponding record from the course_enrollment table, you can raise an exception or treat it as a course which has no students enrolled.

We accept both of these two solutions.

Cheers,

Kai

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