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https://www.evanmiller.org/how-not-to-sort-by-average-rating.html

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DECLARE @Question tinyint = 1;
DECLARE @Answer tinyint = 2;
DECLARE @UpMod tinyint = 2;
DECLARE @DownMod tinyint = 3;
DECLARE @DownWeight int = 3;
DECLARE @z numeric(19, 9) = 1.96;
DECLARE @zz numeric(19, 9) = SQUARE(@z);

WITH TotalUpDownVotesByTags AS (
    SELECT
          Tags.TagName AS Tags
        , COUNT(DISTINCT Posts.Id) AS Posts
        , SUM(IIF(Votes.VoteTypeId = @UpMod, 1, 0)) AS Upvotes
        , SUM(IIF(Votes.VoteTypeId = @DownMod, 1, 0)) AS Downvotes
    FROM Posts
    INNER JOIN PostTypes
        ON Posts.PostTypeId = PostTypes.Id
    INNER JOIN PostTags
        ON (CASE
                WHEN Posts.PostTypeId = @Question THEN Posts.Id
                WHEN Posts.PostTypeId = @Answer THEN Posts.ParentId
            END) = PostTags.PostId
    INNER JOIN Tags
        ON PostTags.TagId = Tags.Id
    LEFT JOIN Votes
        ON Posts.Id = Votes.PostId
    GROUP BY
        Tags.TagName
),
TotalRatingsByTags AS (
    SELECT
          *
        , (CAST(Upvotes AS numeric(19, 9)) + @zz / 2)
            / (CAST(Upvotes + Downvotes * @DownWeight AS numeric(19, 9)) + @zz)
          AS Ratings
    FROM TotalUpDownVotesByTags
)
SELECT
      RANK() OVER (ORDER BY Ratings DESC) AS Ranking
    , *
FROM TotalRatingsByTags
ORDER BY
    Ratings DESC

view current version

edited sep 10

created oct 23 17 Gao