SQL Noob

[eternaloptimist]

Hey all, I'm wondering if my queries are wrong? I'm a noob and will appreciate any help I can get, thanks in advance.

Question

select courses.coursename, students.lastname from students
inner join courses on students.takingcourse = courses.coursecode
where students.lastname = "Murphy";

Relational Algebra

π coursename (σ( lastname = 'Murphy' (students ⨝ courses) ))

Answer

 

[eternaloptimist]

why does the relational algebra answer have TakingCourse = CourseCode?

 

[Kosmik]

Lol. That's just terrible.

 

[rrh]

You are missing a third table - Student_Course_Link(StudentId, CourseCode) - that links students to the courses that they taking.

 

[maumau]

Lol. That's just terrible.

Shame Kosmik, he's a student.

 

[HeftyCrab]

You are missing a third table - Student_Course_Link(StudentId, CourseCode) - that links students to the courses that they taking.

Yup, read up on Bridge entities and many to many relationships.

 

[Kosmik]

Shame Kosmik, he's a student.

I meant more the question than his reply.

 

[eternaloptimist]

Thanks for the help all. I need to work on this area quite a lot.