Divide MAX score by Grade in different tables MySQL - mysql

Question

table a
no name
2001 jon
2002 jonny
2003 mik
2004 mike
2005 mikey
2006 tom
2007 tomo
2008 tommy
table b
code name credits courseCode
A2 JAVA 25 wer
A3 php 25 wer
A4 oracle 25 wer
B2 p.e 50 oth
B3 sport 50 oth
C2 r.e 25 rst
C3 science 25 rst
C4 networks 25 rst
table c
studentNumber grade coursecode
2003 68 A2
2003 72 A3
2003 53 A4
2005 48 A2
2005 52 A3
2002 20 A2
2002 30 A3
2002 50 A4
2008 90 B2
2007 73 B2
2007 63 B3
SELECT a.num, a.Fname,
b.courseName, b.cMAXscore, b.cCode, c.stuGrade
FROM a
INNER JOIN c
ON a.no = c.no
INNER JOIN b
ON c.moduleCode = b.cCode
INNER JOIN b
ON SUM(b.cMAXscore) / (c.stuGrade)
AND b.cMAXscore = c.stug=Grade
GROUP BY a.Fname, b.cMAXscore, b.cCode, b.courseName,c.stuGrade
"calculate and display every student name(a.Fname) and their ID number(a.num) along with their grade (c.grade) versus the coursse name(b.courseName) and the courses max score(b.cMAXscoure). "
I cant figure out how to divide the MAX by the grade, can someone help?

Answer 1

From the specification, it doesn't look like an aggregate function or a GROUP BY would be necessary. But the specification is ambiguous. There's no table definitions (beyond the unfortunate names and some column references).
Definitions of the tables, along with example data and an example of the desired resultset would go a long ways to removing the ambiguity.
Based on the join predicates in the OP query, I'd suggest something like this query, as a starting point:
SELECT a.Fname
, a.num
, c.grade
, b.courseName
, b.cMAXsource
FROM a
JOIN c
ON c.no = a.no
JOIN b
ON b.cCode = c.moduleCode
ORDER
BY a.Fname
, a.num
, c.grade
, b.courseName
, b.cMAXsource
It seems like that would return the specified result (based on my interpretation of the vague specification.) If that's insufficient i.e. if that doesn't return the desired resultset, then in what way does the desired result differ from the result from this query?
(For more help with your question, I suggest you setup a sqlfiddle example with tables and example data. That will make it easier for someone to help you.)
FOLLOWUP
Based on the additional information provided in the question (table definitions and example data...
To get the maximum (highest) grade for a given course, you could use a query like this:
SELECT MAX(c.grade)
FROM c
WHERE c.coursecode = 'A2'
To get the highest grade for all courses:
SELECT c.coursecode
, MAX(c.grade) AS max_grade
FROM c
GROUP BY c.coursecode
ORDER BY c.coursecode
To match the highest grade for each course to each student grade, use that previous query as an inline view in another query. Something like this:
SELECT g.studentNumber
, g.grade
, g.coursecode
, h.coursecode
, h.highest_grade
FROM c g
JOIN ( SELECT c.coursecode
, MAX(c.grade) AS highest_grade
FROM c
GROUP BY c.coursecode
) h
ON h.coursecode = g.coursecode
To perform a calculation, you can use an expression in the SELECT list of the outer query.
For example, to divide the value of one column by another, you can use the division operator:
SELECT g.studentNumber AS student_number
, g.grade AS student_grade
, g.coursecode AS student_coursecode
, h.coursecode
, h.highest_grade
, g.grade / h.highest_grade AS `student_grade_divided_by_highest_grade`
FROM c g
JOIN ( SELECT c.coursecode
, MAX(c.grade) AS highest_grade
FROM c
GROUP BY c.coursecode
) h
ON h.coursecode = g.coursecode
If you want to also return the name of the student, you can perform a join operation to (the unfortunately named) table a. Assuming that studentnumber is UNIQUE in a :
LEFT
JOIN a
ON a.studentnumber = c.studentnumber
And include a.Fname AS student_first_name in the SELECT list.
If you also need columns from table b, then join that table as well. Assuming that coursecode is UNIQUE in b:
LEFT
JOIN b
ON b.coursecode = g.courscode
Then b.credits can be referenced in an expression in the SELECT list.
Beyond that, you need to be a little more explicit about what result should be returned by the query.
If you are after a "total overall grade" for a student, you'd need to specify how that result should be obtained.

Answer 2

Without knowing table definations it is very hard to provide solution to your problem.
Here is my version of what you are trying to look for:
DECLARE #Student TABLE
(StudentID INT IDENTITY,
FirstName VARCHAR(255),
LastName VARCHAR(255)
);
DECLARE #Course TABLE
(CourseID INT IDENTITY,
CourseCode VARCHAR(25),
CourseName VARCHAR(255),
MaxScore INT
);
DECLARE #Grade TABLE
(ID INT IDENTITY,
CourseID INT,
StudentID INT,
Score INT
);
--Student
insert into #Student(FirstName, LastName)
values ('Test', 'B')
insert into #Student(FirstName, LastName)
values ('Test123', 'K')
--Course
insert into #Course(CourseCode, CourseName, MaxScore)
values ('MAT101', 'MATH',100.00)
insert into #Course(CourseCode, CourseName, MaxScore)
values ('ENG101', 'ENGLISH',100.00)
--Grade
insert into #Grade(CourseID, StudentID, Score)
values (1, 1,93)
insert into #Grade(CourseID, StudentID, Score)
values (1, 1,65)
insert into #Grade(CourseID, StudentID, Score)
values (1, 1,100)
insert into #Grade(CourseID, StudentID, Score)
values (2, 1,100)
insert into #Grade(CourseID, StudentID, Score)
values (2, 1,69)
insert into #Grade(CourseID, StudentID, Score)
values (2, 1,95)
insert into #Grade(CourseID, StudentID, Score)
values (1, 2,100)
insert into #Grade(CourseID, StudentID, Score)
values (1, 2,65)
insert into #Grade(CourseID, StudentID, Score)
values (1, 2,100)
insert into #Grade(CourseID, StudentID, Score)
values (2, 2,100)
insert into #Grade(CourseID, StudentID, Score)
values (2, 2,88)
insert into #Grade(CourseID, StudentID, Score)
values (2, 2,96)
SELECT a.StudentID,
a.FirstName,
a.LastName,
c.CourseCode,
SUM(b.Score) AS 'StudentScore',
SUM(c.MaxScore) AS 'MaxCourseScore',
SUM(CAST(b.Score AS DECIMAL(5, 2))) / SUM(CAST(c.MaxScore AS DECIMAL(5, 2))) AS 'Grade'
FROM #Student a
INNER JOIN #Grade b ON a.StudentID = b.StudentID
INNER JOIN #Course c ON c.CourseID = b.CourseID
GROUP BY a.StudentID,
a.FirstName,
a.LastName,
c.CourseCode;

Answer 3

The problem statement doesn't say anything about dividing by the max, I think you're misunderstanding it.
You need to write a subquery that gets the maximum score for each class, using MAX and GROUP BY. You can then join this with the other tables.
SELECT s.name AS student_name, c.name AS course_name, g.grade, m.max_grade
FROM student AS s
JOIN grade AS g ON s.no = g.studentNumber
JOIN course AS c ON c.code = g.courseCode
JOIN (SELECT courseCode, MAX(grade) AS max_grade
FROM grade
GROUP BY courseCode) AS m
ON m.courseCode = c.courseCode
If you did need to divide the grade by the maximum, you can use g.grade/m.max_grade.