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 SQL Reporting by Example Day 3: Getting Good at Grouping Least Popular Subject

Daniel Thor
Daniel Thor
18,137 Points
Posted by Daniel Thor
Daniel Thor
18,137 Points

Benefit of common table expression

What is the benefit of using a common table expression here instead of something like

SELECT SUBJECTS.NAME, COUNT(*) "CT" FROM SUBJECTS JOIN CLASSES ON CLASSES.SUBJECT_ID = SUBJECTS.ID JOIN SCHEDULE ON SCHEDULE.CLASS_ID = CLASSES.ID GROUP BY SUBJECTS.ID ORDER BY "CT" ASC LIMIT 1 ;

Also, in general, is a common table expression often the only method to get the desired results?

This is the type of thing I would like to see cleared up in the videos.

1 Answer

Steven Parker
Steven Parker
231,275 Points
Steven Parker
Steven Parker
231,275 Points

CTE's are usually not the only way to achieve a result, but they can help to make the code significantly more compact and easier to maintain.

The benefits are not so apparent in the simple example presented here, but it serves to illustrate the basic format.