SQL Incorrect SUMS from multiple JOINS - mysql

Question

I'm trying to sum multiple tables using Joins and Sums in MySQL and not having much success.
My Tables (Unnecessary Columns Removed)
Students
idStudent studentname studentyear
1 foobar 11
2 barfoo 11
3 thing 8
Athletics_Results
idResult idStudent points
1 1 14
2 1 11
3 3 7
4 2 9
Team_Results
idTeamResults year points
1 11 9
2 8 8
3 7 14
So let me explain about the tables, because I admit they're poorly named and designed.
Students holds the basic info about each student, including their year and name. Each student has a unique ID.
Athletics_Results stores the results from athletics events. The idStudent column is a foreign key and relates to idStudent in the student column. So student foobar (idStudent 1) has scored 14 and 11 points in the example.
Team_Results stores results from events that more than one student took part in. It just stores the year group and points.
The Aim
I want to be able to produce a sum of points for each year - combined from both athletics_results and team_results. EG:
year points
7 14 <-- No results in a_r, just 14 points in t_r
8 15 <-- 7 points in a_r (idResult 4) and 8 in t_r
11 43 <-- 14, 11, 9 points in a_r and 9 in t_r
What I've tried
For testing purposes, I've not tried combining the a_r scores and t_r scores yet but left them as two columns so I can see what's going on.
The first query I tried:
SELECT students.studentyear as syear, SUM(athletics_results.points) as score, SUM(team_results.points) as team_score
FROM students
JOIN team_results ON students.studentyear = team_results.year
JOIN athletics_results ON students.idStudent = athletics_results.idStudent
GROUP BY syear;
This gave different rows for each year (as desired) but had incorrect SUMS. I learnt this was due to not grouping the joins.
I then created this code:
SELECT studentyear as sYear, teamPoints, AthleticsPoints
FROM students st
JOIN (SELECT year, SUM(tm.points) as teamPoints
FROM team_results tm
GROUP BY year) tr ON st.studentyear = tr.year
JOIN (SELECT idStudent, SUM(atr.points) as AthleticsPoints
FROM athletics_results atr
) ar ON st.idStudent = ar.idStudent
Which gave correct SUMS but only returned one year group row (e.g the scores for Year 11).
EDIT - SQLFiddle here: http://sqlfiddle.com/#!9/dbc16/. This is with my actual test data which is a bigger sample than the data I posted here.

Answer 1

http://sqlfiddle.com/#!9/ad111/7
SELECT tr.`year`, COALESCE(tr.points,0)+COALESCE(SUM(ar.points),0)
FROM Team_Results tr
LEFT JOIN Students s
ON tr.`year`=s.studentyear
LEFT JOIN Athletics_Results ar
ON s.idStudent = ar.idStudent
GROUP BY tr.year
According to your comment and fiddle provided
check http://sqlfiddle.com/#!9/dbc16/3
SELECT tr.`year`, COALESCE(tr.points,0)+COALESCE(SUM(ar.points),0)
FROM (
SELECT `year`, SUM(points) as points
FROM Team_Results
GROUP BY `year`) tr
LEFT JOIN Students s
ON tr.`year`=s.studentyear
LEFT JOIN Athletics_Results ar
ON s.idStudent = ar.idStudent
GROUP BY tr.year

Answer 2

Try this http://sqlfiddle.com/#!9/2bfb1/1/0
SELECT
year, SUM(points)
FROM
((SELECT
a.year, SUM(b.points) AS points
FROM
student a
JOIN at_result b ON b.student_id = a.id
GROUP BY a.year) UNION (SELECT
a.year, SUM(a.points) AS points
FROM
t_result a
GROUP BY a.year)) c
GROUP BY year;
On your data I get:
year points
7 14
8 15
11 43

Answer 3

Can be done in multiple ways. My first thought is:
SELECT idStudent, year, SUM(points) AS totalPoints FROM (
SELECT a.idStudent, c.year, a.points+b.points AS points
FROM students a
INNER JOIN Athletics_Results b ON a.idStudent=b.idStudent
INNER JOIN Team_Results c ON a.studentyear=c.year) d
GROUP BY idStudent,year