Creating a SQL view from tables without UIDs - mysql

Question

I have two tables:
match_rating, which have data on a team's performance in a match. There are naturally two tuples for every matchId (since there are two teams to each match). The PK is matchId, teamId.
event, which has information on events during matches. The PK is an autoincremented UID, and it contains the Foreign Keys match_id and subject_team_id as well.
Now I want to create a new view which counts how many times certain events happen in a match, for each team, with fields like this:
But for the life of me I cannot get around the fact that there are 1) two tuples for each match in the match_rating table, and 2) querying the event table on match_id returns events for both teams.
The closest I got was something like this:
SELECT SUM(
CASE
WHEN evt.event_type_id = 101 THEN 1
WHEN evt.event_type_id = 111 THEN 1
WHEN evt.event_type_id = 121 THEN 1
[etc]
END
) AS 'mid_chances',
SUM(
CASE
WHEN evt.event_type_id = 103 THEN 1
WHEN evt.event_type_id = 113 THEN 1
WHEN evt.event_type_id = 123 THEN 1
[etc]
END
) AS 'right_chances',
mr.tactic,
mr.tactic_skill,
mr.bp,
evt.match_id,
evt.subject_team_id
FROM event evt
JOIN match_rating mr
ON evt.match_id = mr.match_id
WHERE evt.event_type_id BETWEEN 100 AND 104 OR
evt.event_type_id BETWEEN 110 AND 114 OR
evt.event_type_id BETWEEN 120 AND 124 OR
[etc]
GROUP BY evt.match_id
ORDER BY `right_chances` DESC
But still, this counts the events twice, reporting 2 events where there was only 1, 6 for 3 events and so on. I have tried grouping on team_id as well (GROUP BY evt.match_id AND team_id) , but that returns only 2 rows with all events counted.
I hope I have made my problem clear, and it should be obvious that I really need a good tip or two.
Edit for clarity (sorry):
Sample data for match_rating table:
Sample data for the event table:
What I would like to see as the result is this:
That is, two tuples for each match, one for each team, where the types of events that team had is summed up. Thanks so much for looking into this!

Answer 1

Update after comments/feedback
OK.. just to confirm, what you want is
Each row of the output represents a team within a match
Other values (other than match_id and team_id) are sums or other aggregations across multiple rows?
If that is the case, then I believe you should be doing a GROUP BY the match_id and team_id. This should cause the correct number of rows to be generated (one for each match_id/team_id combination). You say in your question that you have tried it already - I suggest reviewing it (potentially after also considering the below).
With your data, it appears that the 'event' table also has a field which indicates the team_id. To ensure you only get the relevant team's events, I suggest your join between match_rating and event be on both fields e.g.,
FROM event evt
JOIN match_rating mr
ON evt.match_id = mr.match_id
AND evt.subject_team_id = mr.team_id
Previous answer - does not answer the question (as per later comments)
Just confirming - the issue is that when you run it, for each match it returns 2 rows - one for each team - but you want to do processing on both teams as one row only?
As such, you could do a few things (e.g., self-join the match rating table to itself, with Team1 ratings and Team2 ratings).
Alternatively, you could modify your FROM to have joins to match_rating twice - where the first has the lower ID for the two teams e.g.,
FROM event evt
JOIN match_rating mr_team1
ON evt.match_id = mr_team1.match_id
JOIN match_rating mr_team2
ON evt.match_id = mr_team2.match_id
AND mr_team1.match_id < mr_team2.match_id
Of course, your processing then needs to be modified to take this into account e.g., one row represents a match, and you have a bunch of data for team1 and similar data for team2. You'd then, I assume, compare the data for team1 columns and team2 columns to get some sort of rating etc (e.g., chance for Team1 to win, etc).