Here's one way, but I've got a feeling you're not going to like it...
Consider the following data DDL's...
CREATE TABLE results
(id INT NOT NULL AUTO_INCREMENT PRIMARY KEY
,homeTeam INT NOT NULL
,awayTeam INT NOT NULL
,homeScore INT NOT NULL
,awayScore INT NOT NULL
);
INSERT INTO results VALUES
(1,1,2,3,2),
(2,3,4,0,1),
(3,2,1,2,0),
(4,4,3,1,0),
(5,3,2,1,2),
(6,2,3,0,2),
(7,1,4,4,1),
(8,4,1,1,2),
(9,1,3,3,0),
(10,3,1,1,0),
(11,4,2,1,0),
(12,2,4,1,2);
From here, we can obtain an intermediate result as follows...
SELECT x.*, COUNT(*) rank
FROM
( SELECT id,hometeam team, CASE WHEN homescore > awayscore THEN 'w' ELSE 'l' END result FROM results
UNION
SELECT id,awayteam, CASE WHEN awayscore > homescore THEN 'w' ELSE 'l' END result FROM results
) x
JOIN
( SELECT id,hometeam team, CASE WHEN homescore > awayscore THEN 'w' ELSE 'l' END result FROM results
UNION
SELECT id,awayteam, CASE WHEN awayscore > homescore THEN 'w' ELSE 'l' END result FROM results
) y
ON y.team = x.team
AND y.id <= x.id
GROUP
BY x.id
, x.team
ORDER
BY team, rank;
+----+------+--------+------+
| id | team | result | rank |
+----+------+--------+------+
| 1 | 1 | w | 1 |
| 3 | 1 | l | 2 |
| 7 | 1 | w | 3 |
| 8 | 1 | w | 4 |
| 9 | 1 | w | 5 |
| 10 | 1 | l | 6 |
| 1 | 2 | l | 1 |
| 3 | 2 | w | 2 |
| 5 | 2 | w | 3 |
| 6 | 2 | l | 4 |
| 11 | 2 | l | 5 |
| 12 | 2 | l | 6 |
| 2 | 3 | l | 1 |
| 4 | 3 | l | 2 |
| 5 | 3 | l | 3 |
| 6 | 3 | w | 4 |
| 9 | 3 | l | 5 |
| 10 | 3 | w | 6 |
| 2 | 4 | w | 1 |
| 4 | 4 | w | 2 |
| 7 | 4 | l | 3 |
| 8 | 4 | l | 4 |
| 11 | 4 | w | 5 |
| 12 | 4 | w | 6 |
+----+------+--------+------+
By inspection, we can see that team 1 has the longest winning streak (3 consecutive 'w's). You can set up a couple of @vars to track this or, if you're slightly masochistic (like me) you can do something slower, longer, and more complicated...
SELECT a.team
, MIN(c.rank) - a.rank + 1 streak
FROM (SELECT x.*, COUNT(*) rank
FROM
( SELECT id,hometeam team, CASE WHEN homescore > awayscore THEN 'w' ELSE 'l' END result FROM results
UNION
SELECT id,awayteam, CASE WHEN awayscore > homescore THEN 'w' ELSE 'l' END result FROM results
) x
JOIN
( SELECT id,hometeam team, CASE WHEN homescore > awayscore THEN 'w' ELSE 'l' END result FROM results
UNION
SELECT id,awayteam, CASE WHEN awayscore > homescore THEN 'w' ELSE 'l' END result FROM results
) y
ON y.team = x.team
AND y.id <= x.id
GROUP
BY x.id
, x.team
) a
LEFT
JOIN (SELECT x.*, COUNT(*) rank
FROM
( SELECT id,hometeam team, CASE WHEN homescore > awayscore THEN 'w' ELSE 'l' END result FROM results
UNION
SELECT id,awayteam, CASE WHEN awayscore > homescore THEN 'w' ELSE 'l' END result FROM results
) x
JOIN
( SELECT id,hometeam team, CASE WHEN homescore > awayscore THEN 'w' ELSE 'l' END result FROM results
UNION
SELECT id,awayteam, CASE WHEN awayscore > homescore THEN 'w' ELSE 'l' END result FROM results
) y
ON y.team = x.team
AND y.id <= x.id
GROUP
BY x.id
, x.team
) b
ON b.team = a.team
AND b.rank = a.rank - 1
AND b.result = a.result
LEFT
JOIN (SELECT x.*, COUNT(*) rank
FROM
( SELECT id,hometeam team, CASE WHEN homescore > awayscore THEN 'w' ELSE 'l' END result FROM results
UNION
SELECT id,awayteam, CASE WHEN awayscore > homescore THEN 'w' ELSE 'l' END result FROM results
) x
JOIN
( SELECT id,hometeam team, CASE WHEN homescore > awayscore THEN 'w' ELSE 'l' END result FROM results
UNION
SELECT id,awayteam, CASE WHEN awayscore > homescore THEN 'w' ELSE 'l' END result FROM results
) y
ON y.team = x.team
AND y.id <= x.id
GROUP
BY x.id
, x.team
) c
ON c.team = a.team
AND c.rank >= a.rank
AND c.result = a.result
LEFT
JOIN (SELECT x.*, COUNT(*) rank
FROM
( SELECT id,hometeam team, CASE WHEN homescore > awayscore THEN 'w' ELSE 'l' END result FROM results
UNION
SELECT id,awayteam, CASE WHEN awayscore > homescore THEN 'w' ELSE 'l' END result FROM results
) x
JOIN
( SELECT id,hometeam team, CASE WHEN homescore > awayscore THEN 'w' ELSE 'l' END result FROM results
UNION
SELECT id,awayteam, CASE WHEN awayscore > homescore THEN 'w' ELSE 'l' END result FROM results
) y
ON y.team = x.team
AND y.id <= x.id
GROUP
BY x.id
, x.team
) d
ON d.team = a.team
AND d.rank = c.rank + 1
AND d.result = a.result
WHERE a.result = 'w'
AND b.id IS NULL
AND c.id IS NOT NULL
AND d.id IS NULL
GROUP
BY a.team
, a.rank
ORDER
BY streak DESC
LIMIT 1;
+------+--------+
| team | streak |
+------+--------+
| 1 | 3 |
+------+--------+
Note that this doesn't account for individual match ties (a modest change to the repeated subquery), nor if two teams have longest winning streaks of equal length (requiring a JOIN of everything here back on itself!).
