在 data.stackexchange 中获取每月的帖子数

Question

我正在尝试获取每月的帖子总数

WITH QuestStatsByMonth  AS (
    SELECT  DATEADD (month, DATEDIFF (month, 0, q.CreationDate), 0) AS [Month],
    t.TagName,
    SUM (q.Score)               AS TotalScore,
    q.Id                        AS id

    FROM        Posts           q
    INNER JOIN  PostTags        pt
    ON          q.Id            = pt.PostId
    INNER JOIN  Tags            t
    ON          t.Id            = pt.TagId

    WHERE       q.PostTypeId    = 1
    AND         t.TagName       IN ('perl6')

    GROUP BY    DATEADD (month, DATEDIFF (month, 0, q.CreationDate), 0),
                t.TagName
)
SELECT
q.[Month], q.TagName + ' questions' AS [Tag], COUNT(q.id) AS Qs

FROM        QuestStatsByMonth   q
LEFT JOIN   QuestStatsByMonth   h
ON          h.[Month]           <= q.[Month]
AND         h.TagName           = q.TagName
GROUP BY    q.[Month], q.TagName
ORDER BY    q.[Month], q.TagName

但这会发出

Column 'Posts.Id' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

我试图在 WITH 语句中生成 COUNT，但错误出在其他地方。有什么想法吗？

Answer 1

您需要用 agg 函数包装 q.id：

WITH QuestStatsByMonth  AS (
    SELECT DATEADD (month, DATEDIFF (month, 0, q.CreationDate), 0) AS [Month],
    t.TagName,
    SUM (q.Score)               AS TotalScore,
    COUNT(q.Id)                 AS id

    FROM  Posts           q
    JOIN  PostTags        pt
      ON  q.Id            = pt.PostId
    JOIN  Tags            t
      ON  t.Id            = pt.TagId
    WHERE q.PostTypeId    = 1
      AND t.TagName       IN ('perl6')
    GROUP BY    DATEADD (month, DATEDIFF (month, 0, q.CreationDate), 0),
                t.TagName
)
SELECT
  q.[Month], q.TagName + ' questions' AS [Tag],
  SUM(q.id) AS Qs
FROM        QuestStatsByMonth   q
LEFT JOIN   QuestStatsByMonth   h
  ON          h.[Month]           <= q.[Month]
  AND         h.TagName           = q.TagName
GROUP BY    q.[Month], q.TagName
ORDER BY    q.[Month], q.TagName;

SEDE Demo

Answer 2

去掉这些位：

SUM (q.Score)               AS TotalScore,

和

GROUP BY    DATEADD (month, DATEDIFF (month, 0, q.CreationDate), 0),
            t.TagName

在您的 CTE 中，您只需过滤问题。如果分组是您在主查询中所做的事情，您实际上不应该分组。分组使得无法select q.Id：你要求每个month/tag一行，但每个month/tag中通常有多个问题ID。您可以只删除 TotalScore 而无需替换它，因为您无论如何都不会使用它。

Answer 3

我删除了 LEFT JOIN 部分。

WITH QuestStatsByMonth  AS (
    SELECT DATEADD (month, DATEDIFF (month, 0, q.CreationDate), 0) AS [Month],
    t.TagName,
    SUM (q.Score)               AS TotalScore,
    COUNT(q.Id)                        AS id

    FROM  Posts           q
    JOIN  PostTags        pt
      ON  q.Id            = pt.PostId
    JOIN  Tags            t
      ON  t.Id            = pt.TagId
    WHERE q.PostTypeId    = 1
      AND t.TagName       IN ('perl6')
    GROUP BY    DATEADD (month, DATEDIFF (month, 0, q.CreationDate), 0),
                t.TagName
)
SELECT
  q.[Month], q.TagName + ' questions' AS [Tag],
  COUNT(q.id) AS Qs
FROM        QuestStatsByMonth   q
GROUP BY    q.[Month], q.TagName
ORDER BY    q.[Month], q.TagName

看起来像你问的。

在 data.stackexchange 中获取每月的帖子数

Get number of posts per month in data.stackexchange

sql

tsql

sql-server

data.stackexchange.com