Question

I pull a range (e.g. limit 72, 24) of games from a database according to which have been voted most popular. I have a separate table for tracking game data, and one for tracking individual votes for a game (rating from 1 to 5, one vote per user per game). A game is considered “most popular” or “more popular” when that game has the highest average rating of all the rating votes for said game. Games with less than 5 votes are not considered. Here is what the tables look like (two tables, “games” and “votes”):

games:
gameid(key)
gamename
thumburl

votes:
userid(key)
gameid(key)
rating

Now, I understand that there is something called an “index” which can speed up my queries by essentially pre-querying my tables and constructing a separate table of indices (I don’t really know.. that’s just my impression).

I’ve also read that mysql operates fastest when multiple queries can be condensed into one longer query (containing joins and nested select statements, I presume).

However, I am currently NOT using an index, and I am making multiple queries to get my final result.

What changes should be made to my database (if any — including constructing index tables, etc.)? And what should my query look like?

Thank you.

Answer 1

Your query that calculates the average for every game could look like:

SELECT gamename, AVG(rating)
FROM games INNER JOIN votes ON games.gameid = votes.gameid
GROUP BY games.gameid
HAVING COUNT(*)>=5 
ORDER BY avg(rating) DESC
LIMIT 0,25

You must have an index on gameid on both games and votes. (if you have defined gameid as a primary key on table games that is ok)