Select all combinations - mysql

Question

It’s pretty difficult to explain what I try to accomplish with just word. So I tried to make an example which reflects my real project. I have a group of people (Peter, Aaron, Mark, Alicia, Cleo and Mike) who play games (A, B and C) against each other. What I would like to do with my query is to get all combination who played against each other for the particular games.
So for example:
Peter played one A game vs Aaron he won in 3 rounds - > Peter - Aaron - A - 1 - 5 - 1
Mike played two C games vs Cleo and lost twice, in 3 and 4 rounds ->
Mike - Cleo - C - 0 - 3.5 - 2
Example table games:
id playRound player game win rounds
1 1 Peter A 1 5
2 1 Aaron A 0 5
3 1 Alicia B 0 3
4 1 Mark B 1 3
5 1 Mike C 0 4
6 1 Cleo C 1 4
7 2 Alicia A 1 5
8 2 Mark A 0 5
9 2 Peter B 1 3
10 2 Mark B 0 3
11 2 Mike C 0 3
12 2 Cleo C 1 3
13 3 Alicia A 0 4
14 3 Mark A 1 4
15 3 Peter B 0 4
16 3 Aaron B 1 4
17 3 Alicia C 1 5
18 3 Cleo C 0 5
End result:
playerONE playerTwo game avgWinRateOne avgRounds Number
Peter Aaron A 1 5 1
Peter Aaron B 1 3 1
Peter Mark B 0 4 1
Alicia Mark A 0.5 4.5 2
Alicia Mark B 0 3 1
Alicia Cleo C 1 5 1
Mike Cleo C 0 3.5 2
I'm fiddling with this but I Have no idea what im doing
SELECT *
FROM (
SELECT *
FROM `testtable`
WHERE `game` = 'A'
GROUP BY `gameId` , `game` , `player`
)tmp1, (
SELECT *
FROM `testtable`
WHERE `game` = 'A'
GROUP BY `gameId` , `game` , `player`
)tmp2

Answer 1

I think maybe you want this query:
select p1.player, p2.player, p1.game, avg(p1.win), avg(p1.rounds), count(*)
from games p1
inner join games p2
on p1.playround = p2.playround
and p1.game = p2.game
and p1.player != p2.player
group by p1.player, p2.player, p1.game;
It's a relatively basic join, where we associate the games table with itself, to get our game pairings, we can them group by those pairings, in order to use aggregate functions to calculate the averages, and number of games played.
Running it on your sample data gives this output:
mysql> select p1.player, p2.player, p1.game, avg(p1.win), avg(p1.rounds), count(*)
-> from games p1
-> inner join games p2
-> on p1.playround = p2.playround
-> and p1.game = p2.game
-> and p1.player != p2.player
-> group by p1.player, p2.player, p1.game;
+--------+--------+------+-------------+----------------+----------+
| player | player | game | avg(p1.win) | avg(p1.rounds) | count(*) |
+--------+--------+------+-------------+----------------+----------+
| Aaron | Peter | A | 0.0000 | 5.0000 | 1 |
| Aaron | Peter | B | 1.0000 | 4.0000 | 1 |
| Alicia | Cleo | C | 1.0000 | 5.0000 | 1 |
| Alicia | Mark | A | 0.5000 | 4.5000 | 2 |
| Alicia | Mark | B | 0.0000 | 3.0000 | 1 |
| Cleo | Alicia | C | 0.0000 | 5.0000 | 1 |
| Cleo | Mike | C | 1.0000 | 3.5000 | 2 |
| Mark | Alicia | A | 0.5000 | 4.5000 | 2 |
| Mark | Alicia | B | 1.0000 | 3.0000 | 1 |
| Mark | Peter | B | 0.0000 | 3.0000 | 1 |
| Mike | Cleo | C | 0.0000 | 3.5000 | 2 |
| Peter | Aaron | A | 1.0000 | 5.0000 | 1 |
| Peter | Aaron | B | 0.0000 | 4.0000 | 1 |
| Peter | Mark | B | 1.0000 | 3.0000 | 1 |
+--------+--------+------+-------------+----------------+----------+
14 rows in set (0.00 sec)