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I ran into a situation where a weak entity happens to have attributes which are primary keys in two different entities.

My situation is like:

Strong entities:

--Course
-Course_Num(P.K)
-Title
-Credits

--Semester
-Semester_id(P.K)
-StartDate
-EndDate

Now a weak entity CoursesOffered has attributes as follows

--CoursesOffered
  -Course_Num
  -Semester_id
  -Instructor_Name

So my question is, can this weak entity have identifying relationship with above two strong entities, since the courses offered will be depending on the rows of two strong entities. Please help I am stuck if this would be correct.

  • If only one instructor may be related to (Course, Semester) pair which is unique then everything looks safe. Except not Instructor_Name but Instructor_id which is referenced to Instructors table. – Akina Feb 25 at 6:39

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