On Saturday, July 20, 2019, Karen Goh <
karenworld@xxxxxxxxx> wrote:
> > I realised now that the keys are not created and perhaps that is why the
> join query is not working out.
The presence or absence of PK and FK meta data is not the problem here. A properly written query will work whether those are present or not. What is does indicate is a failure to understand the query, model, or both. You should probably show more of both to receive better help.
>> In this case, what should I do then since I can't make tutor_id a Primary key but yet it has to reference s_tutor.tutor_id as foreign key?
What is this s_tutor thing you’ve newly added to the problem space?
Your tutor_id PK exists on the TUTOR TABLE. Your tutor_subject.tutor_id FKs to that. Your SUBJECT TABLE has a subject_id PK. Your tutor_subject.subject_id field FKs to that. If you need something to FK to the tutor_subject table it should also contain both tutor_id and subject_id fields (yes, you can create a make believe tutor_subject_id PK field and link to that - you shouldn’t).
If you need an FK for tutor_id its point to the TUTOR TABLE. If you don’t have a TUTOR TABLE you’ve discovered the flaw in your model.
David J.
