Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Databases

Muhittin Palamutçu
Muhittin Palamutçu
1,890 Points
Posted by Muhittin Palamutçu
Muhittin Palamutçu
1,890 Points

I need some help for my Sql Query

Student(id(key),name) Professor(id,name,deperment) Course(number(key),instructorID,title,credits,roomNumber) Enroll(StudentID(key),courseNumber(key) Room(number(key),capacity)

I need to find course number and their titles that have more than 40 students enrolled?

SELECT C.number,C.titles FROM Course C,Enroll E WHERE C.number=E.courseNumber AND E.count(StudentID)>40;

I wrote something like that but ı know it's false. If you help me ı will be pleased.

2 Answers

KRIS NIKOLAISEN
KRIS NIKOLAISEN
54,971 Points

Try this:

SELECT enroll.courseNumber, course.title FROM course, enroll WHERE course.number = enroll.courseNumber GROUP BY enroll.courseNumber, course.title HAVING ( ( COUNT( enroll.studentID ) > 40 ) )
Steven Parker
Steven Parker
231,269 Points
Steven Parker
Steven Parker
231,269 Points

It looks like you're getting close, here's a couple of hints:

  • a GROUP BY might be handy when counting things that have something in common
  • another way to filter when using grouping is with the HAVING keyword