Take the 2-minute tour ×
Database Administrators Stack Exchange is a question and answer site for database professionals who wish to improve their database skills and learn from others in the community. It's 100% free, no registration required.

I have to plan a plan tree based on relational algebra.My question is that at some point I have a SORT ORDER BY the output of a join, so how do you represent group by in relational algebra.

share|improve this question
Check this wiki article and look under the sections aggregation: en.wikipedia.org/wiki/Relational_algebra#Aggregation. It mentions a way to group by. Otherwise there's also cs.ulb.ac.be/public/_media/teaching/infoh417/sql2alg_eng.pdf which shows some group by. Maybe that can guide you in the direction –  Allan S. Hansen Dec 13 '13 at 10:52
Thanks very much you've answered my question –  Phil_Charly Dec 13 '13 at 10:58

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.