Use the document structure described in Exercise 15.23 to formulate the following queries in XQuery:
a. List all classes (identi?ed by a course code and semester) where every student received a B or higher.
b. List all students who never received less than a B.
a.
DECLARE FUNCTION classesFromTranscripts($elts AS element()*) AS element()*
{
FOR $e IN $elts
RETURN
{ $e//CrsCode, $e//Semester }
}
{
LET $transcripts := doc("http://xyz.edu/transcript.xml")
FOR $c IN
distinct-values(classesFromTranscripts($transcripts//tuple))
LET $grades :=
doc("http://xyz.edu/transcript.xml")
//tuple[CrsCode/@value=$c/CrsCode/@value
and Semester/@value=$c/Semester/@value]
/Grade/@value
WHERE EVERY $g IN $grades
SATISFIES numericGrade($g) >= numericGrade("B")
RETURN $c
}
b.
DECLARE FUNCTION classesFromTranscripts($elts AS element()*) AS element()*
{
FOR $e IN $elts
RETURN
{ $e//CrsCode, $e//Semester }
}
{
LET $transcripts := doc("http://xyz.edu/transcript.xml")
FOR $sid IN
distinct-values(classesFromTranscripts($transcripts//tuple)),
$s IN doc("http://xyz.edu/student.xml")
//tuple[Id/@value=$sid/StudId/@value]
LET $grades :=
$transcripts//tuple[StudId/@value=$sid/StudId/@value]/Grade/@value
WHERE EVERY $g IN $grades
SATISFIES numericGrade($g) >= numericGrade("B")
RETURN $s
}
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