sql - Average of Sum minus Minimum -


hey guys, have sql statement grabs grades of different activity types (homework, quiz, etc), , if there's drop lowest type, drops, else, remains. errors below sql code.

select     student.firstname, student.lastname, 'grades' =            case                when grades.activitytype = 'homework'                 case when policy.drop_hw = 1                     (avg(sum(grades.grade) - min(grades.grade))) * (policy.homework / 100)                 else                     (avg(grades.grade) * (policy.homework / 100))                 end             end,  course.coursenum, course.sectnum, grades.activitytype  ...

here errors i'm getting:

- cannot perform aggregate function on expression containing aggregate or subquery. - column 'policy.drop_hw' invalid in select list because not contained in either aggregate function or group clause.

look analytical functions. (so question, oracle documentation).

something this:

avg(grades.grade) on (partition grades.student_id) avg_of_grades

and:

(avg(sum(grades.grade) - min(grades.grade))) on (partition grades.student_id) avg_grades_with_drop

set partitioning whatever makes sense in case; can't tell since omitted from ... in example.

you can use column aliases in calculations inside case statement.


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