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DECLARE @Question tinyint = 1;
DECLARE @Answer tinyint = 2;
DECLARE @UpMod tinyint = 2;
DECLARE @DownMod tinyint = 3;
DECLARE @DownWeight int = 5;
DECLARE @z numeric(19, 9) = 1.96;
DECLARE @zz numeric(19, 9) = SQUARE(@z);

WITH TotalUpDownVotesByTags_VIEW AS (
    SELECT
          Tags.TagName
        , PostTypes.Name AS PostType
        , COUNT(DISTINCT Posts.Id) AS PostCount
        , SUM(CASE
                  WHEN Votes.VoteTypeId = @UpMod THEN 1
                  ELSE 0
              END)
          AS PostUpvotes
        , SUM(CASE
                  WHEN Votes.VoteTypeId = @DownMod THEN 1
                  ELSE 0
              END)
          AS PostDownvotes
    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, PostTypes.Name
)

SELECT
      TagName
    , PostType
    , PostCount
    , PostUpvotes
    , PostDownvotes
    , (CAST(PostUpvotes AS numeric(19, 9)) + @zz / 2)
          / (CAST(PostUpvotes + PostDownvotes * CASE WHEN PostType = 'Answer' THEN @DownWeight ELSE 1 END AS numeric(19, 9)) + @zz)
      AS PostRatings
FROM TotalUpDownVotesByTags_VIEW
ORDER BY PostRatings DESC;

view current version

edited sep 10

created jan 30 18 Gao