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

Daniel Thor
Daniel Thor
18,041 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
217,469 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.