Consider a document that contains a list of professors (name, Id, department Id) and a separate list of classes taught (professor Id, course code, semester). Use aggregate functions of XQuery to produce the following documents:

a. A list of professors (name, Id) with the number of di?erent courses taught by each professor.
b. A list of departments (department Id) along with the number of di?erent courses ever taught by the professors in them. (The same course taught in di?erent semesters or a course taught in the same semester by di?erent professors is counted as one.)

a. Assume that the document consists of two elements, Professors and Classes, which in turn are lists of elements Professor and Class, respectively.





{

     FOR $p IN

            doc("http://xyz.edu/profs-courses.xml")//Professor

     LET $courses := -- All courses ever taught by $p

                 distinct-values(

                       doc("http://xyz.edu/profs-courses.xml")

                                                   //Class[ProfId=$p/Id]/CrsCode

                                 )

    RETURN $p count($courses)

}





{

     LET $depts :=

          distinct-values(doc("http://xyz.edu/profs-courses.xml")//DeptId)

     FOR $d IN $depts

     LET $courses := { -- All courses ever taught by $d

            FOR $p IN doc("http://xyz.edu/profs-courses.xml")

                                                        //Professor[DeptId=$d/DeptId],

                    $c IN doc("http://xyz.edu/profs-courses.xml")

                                                        //Class[ProfId=$p/Id]/CrsCode

            RETURN $c

                                    }

    RETURN $d count(distinct-values($courses))

}