Hey everyone, I’m taking a database class and I’m stuck on this tricky problem. We’ve got these tables:
STUDENTS (Sno, Sname, Gender, Age)
COURSES (Cno, Cname)
ENROLLMENT (Sno, Cno, Grade)
I need to write an SQL query to find the names of students who are taking all the courses offered. I’m not sure how to approach this. Should I use a subquery? Or maybe some kind of join? I’ve tried a few things but nothing seems to work.
Can anyone give me a hint or point me in the right direction? I don’t want the full answer, just some guidance on how to tackle this. Thanks in advance for any help!
Greetings Iris_92Paint,
Your question touches on an advanced SQL concept. One approach you might consider is using a combination of COUNT and GROUP BY. The idea is to compare the count of courses each student is enrolled in with the total number of courses offered.
Here’s a general outline:
- Get the total number of courses.
- Count the courses each student is enrolled in.
- Compare these counts.
You could start by writing a query to get the total course count, then nest this within a larger query that counts each student’s enrollments. The key is to filter for students whose course count matches the total.
This method avoids complex operations like division or NOT EXISTS, which can be harder to grasp initially. It’s a more straightforward counting approach that might be easier to implement and understand.
Have you tried anything along these lines yet? Let me know if you need more clarification on this strategy.
hey iris, tricky one indeed! have u considered using division? it’s perfect for finding “all” scenarios. basically, u wanna divide the set of all courses by the courses each student’s taking. if the result is empty, that student’s taking everything. give it a shot and lemme know how it goes!
Hey Iris_92Paint! That’s a really interesting problem you’ve got there. 
I love a good database challenge!
Have you thought about using a NOT EXISTS approach? It might be a neat way to tackle this. The idea would be to find students who don’t have any courses that they’re not enrolled in. Sounds a bit backwards, right? But it could work!
What if you tried something like checking for students where there doesn’t exist a course they’re not taking? You could start with selecting from STUDENTS, then use a subquery to check against COURSES and ENROLLMENT.
Just brainstorming here, but what do you think about that approach? Have you tried anything similar yet? I’m super curious to hear what you’ve attempted so far and what roadblocks you’ve hit. Maybe we could bounce some ideas around?