MySQL update table with values from same table - mysql

Question

I have a 4 column table, the primary key is a composite of id, gameId and flag.
id | gameId | score | flag
--------------------------
1 | 1 | 10 | 1
1 | 1 | 20 | 0
2 | 1 | 1 | 0
1 | 2 | 10 | 1
3 | 2 | 1 | 0
I need to update the table so that:
All of gameId 2 scores are added to gameId 1 where the id and flag is the same.
(e.g. row 1 would have a score of 20 by adding the scores of row 1 and row 4)
If the above happens the gameId 2 row needs to be deleted.
Where the above isn't found (e.g. there is a row where the gameId is 2 but the id and flag don't match another row), the gameId can just be changed to 1.
So my table after the SQL is complete should look like this:
id | gameId | score | flag
--------------------------
1 | 1 | 20 | 1
1 | 1 | 20 | 0
2 | 1 | 1 | 0
3 | 1 | 1 | 0
How can I write this in SQL?
Thanks :)

Answer 1

think this going to work:
Try 1
UPDATE score_list AS t2
LEFT JOIN score_list AS t1 ON
(t1.id = t2.id AND t1.flag = t2.flag AND t1.gameId = 1)
SET
t1.score = t1.score + t2.score,
t2.gameId = IF(t1.gameId IS NULL, 1, t2.gameId)
WHERE t2.gameId = 2;
DELETE FROM score_list WHERE gameId = 2;
Try 2
# add scores to gameId = 1
UPDATE score_list AS t2
LEFT JOIN score_list AS t1 ON
(t1.id = t2.id AND t1.flag = t2.flag AND t1.gameId = 1)
SET
t1.score = t1.score + t2.score
WHERE t2.gameId = 2;
# try to move gameID 2 to gameId 1, using ignore to allow rows to fail, as gameId alredy exists
UPDATE IGNORE score_list SET gameId = 1 WHERE gameId = 2;
# delete all not updated rows from last query
DELETE FROM score_list WHERE gameId = 2;