MySQL 权重评级

我想根据票数创建一个权重的评级。 因此，1 票 5 票不可能比 4 票 4 票更好。

我找到了这个数学形式：

bayesian = ( (avg_num_votes * avg_rating) + (this_num_votes * this_rating) ) / (avg_num_votes + this_num_votes)

我如何进行 MySQL SELECT 来获取最佳评分图像的 ID。

我有一个用于图像的表和一个用于投票的表

VOTING:

id
imageID
totalVotes
avgVote

我想我必须用 SELECT in SELECT 来做到这一点，但是怎么做呢？

第一步是计算avg_num_votes and avg_rating:

SELECT
  SUM(totalVotes)/COUNT(*) AS avg_num_votes,
  SUM(avgVote)/COUNT(*) AS avg_rating
FROM voting;

如果您可以忍受小错误，那么偶尔计算一下就足够了。

现在，使用您的公式和上面的值，您可以运行称重查询。作为一个小的优化我预先计算avg_num_votes * avg_rating并称之为avg_summand

SELECT
  voting.*, -- or whatever fields you need
  ($avg_summand+totalVotes*avgVote)/($avg_num_votes+totalVotes) AS bayesian
FROM voting
ORDER BY  bayesian DESC
LIMIT 1;

Edit

您可以将其作为联接运行：

SELECT
  voting.*, -- or whatever fields you need
  (avg_num_votes*avg_rating+totalVotes*avgVote)/(avg_num_votes+totalVotes) AS bayesian
FROM voting,
(
  SELECT
    SUM(totalVotes)/COUNT(*) AS avg_num_votes,
    SUM(avgVote)/COUNT(*) AS avg_rating
  FROM voting AS iv
) AS avg
ORDER BY  bayesian DESC
LIMIT 1;

但这将计算每个查询的总和和平均值——称之为性能炸弹。