Question

I have 2 databases (users, userRankings) for a system that needs to have rankings updated every 10 minutes. I use the following code to update these rankings which works fairly well, but there is still a full table scan involved which slows things down with a few hundred thousand users.

mysql_query("TRUNCATE TABLE userRankings");
mysql_query("INSERT INTO userRankings (userid) SELECT id FROM users ORDER BY score DESC");
mysql_query("UPDATE users a, userRankings b SET a.rank = b.rank WHERE a.id = b.userid");

In the userRankings table, rank is the primary key and userid is an index. Both tables are MyISAM (I’ve wondered if it might be beneficial to make userRankings InnoDB).

Answer 1

Try something like this, it should give you the same effect without needing to build a separate table. (my MySql is a bit rusty, but this should work OK)

select @rownum:=@rownum+1 ‘rank’, a.id 
from player a, (SELECT @rownum:=0) r 
order by score desc