database structure for ranking system

Question

I'm making a PHP battle system, and need to sort out the ranking.

How I want it to work is say there's 100 players, and you're rank 90. You can challenge players 5 ranks above, so say you challenge and beat the player in rank 85, then YOU become 85 and he becomes 86.

I'm not sure how to do this with a database though. How to set it out, or store rank. Obviously I can't save a field with your 'rank' since if you win it'd have to edit every single players rank below you in the database, wouldn't it?

Any ideas would be helpful.

Answer 1

I recommend you do keep a rank field and relax the bottleneck in the queries:

In your example use something like

UPDATE players 
SET rank=IF(playerid=<id-of-challengin-player>,rank-5,rank+1) 
WHERE rank>=85 AND rank<=90

This will change ranks

old   new
85    86
86    87
87    88
88    89
89    90
90    85

which looks like what you want, but uses a single query, that can leverage an index and touches only 6 rows.

Edit

To facilitate maintenance (fix rank numbers, if there are holes etc.), run

CREATE VIEW players_by_rank AS 
SELECT * FROM players ORDER BY rank 

once, then use

UPDATE (SELECT @newrank:=0) AS init, players_by_rank 
SET score=(@newrank:=@newrank+1)

to close gaps in the table. Mind that this touches all rows!

Answer 2

你确实可以在数据库中有一个排名栏并按以下方式更新： update yourtable set playerRank=playerRank+1 where playerRank>85然后将获胜玩家更新为playerRank 85.这可能会击中大量记录，但它这不会是数据库的沉重代价。

Answer 3

Since the 'rank' you describe is not based on any other rules, such as points.. something that can be calculated, you must store this rank everywhere.

And yea, that does imply that you need to update a whole bunch of records every time; but since you mention you can only challenge up to 5 positions ahead of you, this also implies that you only ever have to update 6 records every time.. (no big deal)

90 -> 85
89 -> 90
88 -> 89
87 -> 88
86 -> 87
85 -> 86