Join Example (cont)
List names of students in all subjects, arranged by subject.
SQL query to provide this information:
select E.subj, S.name
from Student S, Enrolled E
where S.id = E.stude
order by E.subj, S.name;
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And its relational algebra equivalent:
Sort[subj] ( Project[subj,name] ( Join[id=stude](Student,Enrolled) ) )
To simplify formulae, we denote Student by S and Enrolled by E
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