为什么这个平均值计算不正确？

Question

所以我有两个程序

CREATE PROCEDURE GetAnswersByPartner 
    @pid UNIQUEIDENTIFIER, -- partner id
    @sid INT -- survey id
AS
BEGIN
    SELECT Sections.title AS section_title,
    Subsections.title AS subsection_title,
    Questions.id AS question_id,
    Questions.qtext AS question_text,
    Answers.val AS answer_val 
    FROM Partners
    INNER JOIN Questions ON 1 = 1
    INNER JOIN Subsections ON Subsections.id = Questions.subsection_id
    INNER JOIN Sections ON Sections.id = Subsections.section_id
    INNER JOIN Surveys ON Sections.survey_id = Surveys.id
    LEFT JOIN Answers ON Answers.partner_id = Partners.id
            AND Answers.question_id = Questions.id
    WHERE Partners.id = @pid AND Surveys.id=@sid
    ORDER BY Sections.id ASC
END

和

CREATE PROCEDURE GetSectionAverages
    @partner_id UNIQUEIDENTIFIER,
    @survey_id INT
AS
    BEGIN
        SELECT S.title, AVG(A.val)   
        FROM 
            Sections AS S INNER JOIN Subsections AS SS ON S.Id=SS.section_id
                          INNER JOIN Questions AS Q ON SS.section_id=Q.subsection_id
                          INNER JOIN Answers AS A ON A.question_id=Q.id
                          INNER JOIN Partners AS P ON A.partner_id=P.id
            WHERE S.survey_id=@survey_id AND P.id=@partner_id
            GROUP BY S.title
    END

我无法弄清楚平均值计算错误的原因。

例如，您可以在下面的屏幕截图中看到EXEC GetAnswersByPartner @pid='cd2c53e2-3bd4-451c-8451-6953b9cc7c8b', @sid=1;

部分中"Partner Growth"的结果

当我运行

时，这是计算到100的平均值

EXEC GetSectionAverages @partner_id='cd2c53e2-3bd4-451c-8451-6953b9cc7c8b', @survey_id=1;

知道这里发生了什么吗？

Answer 1

您的第一个查询对Answers表有LEFT JOIN，而您的第二个查询有INNER JOIN。我怀疑存在差异。换句话说，您的第二个查询可能会排除未回答的问题。