Question

I am having a few issues with the below SQL.

SELECT * 
  FROM (SELECT tbrm_Article.ArticleID, 
               tbrm_Article.CountryID,
               tbrm_Article.CategoryID,
               tbrm_Article.Title,
               tbrm_Article.ArticleDetail,
               tbrm_Article.Source,
               tbrm_Article.ArticleDateTimeAdded,
               tbrm_Article.ViewCount,
               tbrm_Article.CommentCount,
               tbrm_CountryList.CountryName AS CountryName,
               tbrm_CountryList.CountryImage AS CountryImage,
               tbrm_CategoryList.CategoryName AS CategoryName,
               tbrm_CategoryList.CategoryImage AS CategoryImage,
               aspnet_Users.UserName AS UserName,
               AVG(tbrm_Votes.True) OVER() AS Truth,
               AVG(tbrm_Votes.False) OVER() AS False,
               ROW_NUMBER() OVER (ORDER BY tbrm_Article.ArticleDateTimeAdded DESC) AS RowRank      
          FROM tbrm_Article 
          JOIN tbrm_CountryList ON tbrm_Article.CountryID = tbrm_CountryList.CountryID 
          JOIN tbrm_CategoryList ON tbrm_Article.CategoryID = tbrm_CategoryList.CategoryID 
          JOIN aspnet_Users ON tbrm_Article.UserID = aspnet_Users.UserID 
          JOIN tbrm_Votes ON tbrm_Article.ArticleID = tbrm_Votes.ArticleID)  Article
   WHERE Article.RowRank > @PageIndex AND RowRank <= (@PageIndex + @PageSize)
ORDER BY Article.ArticleDateTimeAdded DESC

Everything works fine apart from the two AVG statements. Instead of averaging only one applicable relevant article id it is returning the average for the whole votes table of values. Any ideas of the best way to fix this? I am using SQL Server 08.

Answer 1

If you use an aggregate function, such as avg, you need to use partition by in your over clause, or include the columns selected that aren’t aggregates in your group by clause.

Like so:

SELECT * FROM

(

SELECT
tbrm_Article.ArticleID, 
tbrm_Article.CountryID,
tbrm_Article.CategoryID,
tbrm_Article.Title,
tbrm_Article.ArticleDetail,
tbrm_Article.Source,
tbrm_Article.ArticleDateTimeAdded,
tbrm_Article.ViewCount,
tbrm_Article.CommentCount,
tbrm_CountryList.CountryName AS CountryName,
tbrm_CountryList.CountryImage AS CountryImage,
tbrm_CategoryList.CategoryName AS CategoryName,
tbrm_CategoryList.CategoryImage AS CategoryImage,
aspnet_Users.UserName AS UserName,
AVG(tbrm_Votes.True) AS Truth,
AVG(tbrm_Votes.False) AS False,
ROW_NUMBER() OVER (ORDER BY tbrm_Article.ArticleDateTimeAdded DESC) AS RowRank

FROM

tbrm_Article INNER JOIN
    tbrm_CountryList ON tbrm_Article.CountryID = tbrm_CountryList.CountryID INNER JOIN
    tbrm_CategoryList ON tbrm_Article.CategoryID = tbrm_CategoryList.CategoryID INNER JOIN
    aspnet_Users ON tbrm_Article.UserID = aspnet_Users.UserID INNER JOIN
    tbrm_Votes ON tbrm_Article.ArticleID = tbrm_Votes.ArticleID

GROUP BY

tbrm_Article.ArticleID, 
tbrm_Article.CountryID,
tbrm_Article.CategoryID,
tbrm_Article.Title,
tbrm_Article.ArticleDetail,
tbrm_Article.Source,
tbrm_Article.ArticleDateTimeAdded,
tbrm_Article.ViewCount,
tbrm_Article.CommentCount,
tbrm_CountryList.CountryName,
tbrm_CountryList.CountryImage,
tbrm_CategoryList.CategoryName,
tbrm_CategoryList.CategoryImage,
aspnet_Users.UserName


)  Article
WHERE Article.RowRank > @PageIndex AND RowRank <= (@PageIndex + @PageSize)
ORDER BY Article.ArticleDateTimeAdded DESC

If you wanted it just by CountryName, for example, you would drop the group by clause and use:

avg(tbrm_Votes.True) over (partition by tbrm_CountryList.CountryName) as Truth