I can not execute this code on Oracle, the error shows:
"ORA-00979: not a GROUP BY expression"
However, I was able to run it successfully on MySQL.
How does this happen?
SELECT CONCAT(i.lname, i.fname) AS inst_name,
CONCAT(s.lname, s.fname) AS stu_name,
t.avg_grade AS stu_avg_grade
FROM(
SELECT instructor_id, student_id, AVG(grade) as avg_grade, RANK() OVER(PARTITION BY instructor_id ORDER BY grade DESC) AS rk
FROM grade
GROUP BY 1,2) t
JOIN instructor i
ON t.instructor_id = i.instructor_id
JOIN student s
ON s.student_id = t.student_id
WHERE t.rk = 1
ORDER BY 3 DESC
CodePudding user response:
You can't use ordinals like GROUP BY 1,2
in Oracle. In addition, the ORDER BY grade
clause inside your RANK()
function has a problem. Keep in mind that analytic functions evaluate after the GROUP BY
aggregation, so grade
is no longer available. Here is a version which should work without error:
SELECT CONCAT(i.lname, i.fname) AS inst_name,
CONCAT(s.lname, s.fname) AS stu_name,
t.avg_grade AS stu_avg_grade
FROM
(
SELECT instructor_id, student_id, AVG(grade) AS avg_grade,
RANK() OVER (PARTITION BY instructor_id ORDER BY AVG(grade) DESC) AS rk
FROM grade
GROUP BY instructor_id, student_id
) t
INNER JOIN instructor i
ON t.instructor_id = i.instructor_id
INNER JOIN student s
ON s.student_id = t.student_id
WHERE t.rk = 1
ORDER BY t.avg_grade DESC;