Pivoting data in MySQL. - mysql

Question

I'm sure this sort of question has come up before but I've been searching and can't find anything similar to what I need.
Edit: so after some reading this looks like it falls under pivots and uses group concat. If anybody has any insight id really appreciate it.
I have 3 tables (unnecessary fields & data stripped out for simplicity):
Students
id name
------------------
1 John
2 Jane
Tests
id name
------------------
1 Test1
2 Test2
Results
id test_id student_id result
--------------------------------------
1 1 1 90
2 1 2 70
3 2 1 50
4 2 2 95
What I want is to be able to produce a table like this:
Name Average Test1 Test2
-----------------------------------
John 70 90 50
Jane 92.5 70 95
I know how to get the average, and I'm sure I could do this with an ugly set of loops and php logic but I'd like to get the most efficient solution. Any help is greatly appreciated.

Answer 1

SELECT
s.name,
avg(r.result) AS average,
t1.result AS test1,
t2.result AS test2
FROM
students s,
results r,
results t1,
results t2
WHERE
r.student_id = s.id AND
t1.test_id = 1 AND
t1.student_id = s.id AND
t2.test_id = 2 AND
t2.student_id = s.id
GROUP BY s.id;
+------+---------+-------+-------+
| name | average | test1 | test2 |
+------+---------+-------+-------+
| John | 70 | 90 | 50 |
| Jane | 82.5 | 70 | 95 |
+------+---------+-------+-------+
Edit: You can't really make the test columns dynamically based on the contents of the tests table. You can pick specific values to use as columns though.

Answer 2

You'll want to look at the AVG function.

Answer 3

Try This:
mysql> Select s.Name as Name, avg(r.result) as Average
from result as r join Student as s
on r.id=s.id group by (r.id)
you will have something like this:
Name Average
-----------------
John 70
Jane 92.5
You can't put a row as a column, imagine that John have 100000 times the test1, it will no be possible to put it as column.