Making sure my queries are correct, the exam is coming up and thehomework won\'t

Question

Making sure my queries are correct, the exam is coming up and thehomework won't be returned until after the exam :(


Find the names of courses that have at least 2 students with rnogreater than 5.
I was reading up on VIEWS and it seems like they would work nice inthis query or maybe even just a lot of subqueries, but then againthere might be security issues with that. VIews i heard arn'tthat secure becuase someone might be able to modify the internaldata.

   SELECT * from (SELECT cname, count(*) asENROLLEDSTUDENTS
FROM courses C, students S, enrolled E
WHERE S.sid = E.sid and E.cid = C.cid and (SELECT count(*)from students where rno > 5) GROUP cname) AS tempTablewhere ENROLLEDSTUDNETS > 2;


Find the names of students not enrolled in any class
    
   SELECT * FROM students s
WHERE s.sid NOT IN (select sid FROM enrolled);

Sorry its pretty messy.

Explanation / Answer

(selectcid from enrolled where sid in

select sidfrom enrolled);

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