Beregning af rang i PHP/MySQL

Hvis du vil have overordnede placeringer, skal du desværre sortere hele tabellen. Kort sagt kan du ikke kende nogens rangering i tabellen uden at kende de andre rangeringer i tabellen.

Når det er sagt, hvis du er bekymret for ydeevnen, er der en forholdsvis nem løsning her - cache resultatet af din rangeringsforespørgsel (måske ind i en anden MySQL-tabel!), og forespørg det for alle dine læsninger. Når nogen poster en ny score, genberegn din midlertidige tabel. Du kan med jævne mellemrum tømme alle poster under en bestemt rang (f.eks. bliver enhver, der rangerer under 100, fjernet fra resultattabellen) for at holde omregningerne hurtige, da ingen nogensinde ville klatre i rang efter at være blevet slået ned af en højere score.

# Create your overall leaderboards once
create table leaderboards (rank integer primary key, score_id integer, game varchar(65), user_id integer, index game_user_id_idx (game, user_id))


# To refresh your leaderboard, we'll query the ranks for the game into a temporary table, flush old records from scores, then copy
# the new ranked table into your leaderboards table.
# We'll use MySQL's CREATE TABLE...SELECT syntax to select our resultset into it directly upon creation.
create temporary table tmp_leaderboard (rank integer primary key auto_increment, score_id integer, game varchar(65), user_id integer)
  select ID, GameName, UserID, from scores where GameName = '$game' order by score desc;

# Remove old rankings from the overall leaderboards, then copy the results of the temp table into it.
delete from leaderboards where game = '$game';
insert into leaderboards (rank, score_id, game, user_id)
  select rank, score_id, game, user_id from tmp_leaderboard;

# And then clean up the lower scores from the Scores table
delete from scores join tmp_leaderboard on scores.id = tmp_leaderboard.score_id, scores.GameName = tmp_leaderboard.game where tmp_leaderboard.rank < 100;

# And we're done with our temp table
drop table tmp_leaderboard;

Derefter, når du vil læse en rang for et spil:

select rank from leaderboards where game = '$game' and user_id = '$user_id';