Question

我有以下数据库设计：

Employee Table: EmployeeID, Name, OrgCode
Department Table: OrgCode, DepartName
CompleteSurvey Table: ID, RespondantID, QuestionsAnswersID
Questions Table: QuestionID, Question
Answers Table: AnswerID, Answer
QuestionsAnswers Table: ID, QuestionID, AnswerID

每个问题都有不同的多种选择。大多数问题都有相同的选择，例如（同意，不同意）。我想写一个查询，显示问题及其所有选项和每个选项中的参与者数量，即使它是零。 我写了查询，它显示了问题的所有答案，即使没有人选择其中一个答案，但查询在问题列中显示NULL，除了没有参与者的答案，我不知道为什么的。有什么帮助吗？

我的查询：

SELECT     COUNT(DISTINCT dbo.CompleteSurvey.RespondantID) AS [Total Number of Participants], dbo.Answers.Answer, dbo.Questions.Question
FROM         dbo.CompleteSurvey INNER JOIN
                      dbo.QuestionsAnswers ON dbo.CompleteSurvey.QuestionsAnswersID = dbo.QuestionsAnswers.ID INNER JOIN
                      dbo.Questions ON dbo.QuestionsAnswers.QuestionID = dbo.Questions.QuestionID RIGHT OUTER JOIN
                      dbo.Answers ON dbo.QuestionsAnswers.AnswerID = dbo.Answers.AnswerID
GROUP BY dbo.Answers.Answer, dbo.Questions.Question

更新

查询应显示问题中每个部门的参与者人数及其所有答案，那么该如何做？

我的更新查询：

SELECT     COUNT(DISTINCT dbo.CompleteSurvey.RespondantID) AS [Total Number of Participants], dbo.Answers.Answer, dbo.Questions.Question, 
                      dbo.Departments.DepartmentName
FROM         dbo.Employees INNER JOIN
                      dbo.CompleteSurvey ON dbo.Employees.EmployeeID = dbo.CompleteSurvey.RespondantID INNER JOIN
                      dbo.Departments ON dbo.Employees.OrgCode = dbo.Departments.OrgCode RIGHT OUTER JOIN
                      dbo.Questions INNER JOIN
                      dbo.QuestionsAnswers ON dbo.Questions.QuestionID = dbo.QuestionsAnswers.QuestionID INNER JOIN
                      dbo.Answers ON dbo.QuestionsAnswers.AnswerID = dbo.Answers.AnswerID ON dbo.CompleteSurvey.QuestionsAnswersID = dbo.QuestionsAnswers.ID
GROUP BY dbo.Answers.Answer, dbo.Questions.Question, dbo.Departments.DepartmentName

但问题不在于部门。它应该显示每个问题中每个部门的参与者数量及其所有答案，即使其中一个答案没有参与者。

Answer 1

QuestionAnswers是获取答案所需的表格，但由于您使用的是从CompleteSurvey到QuestionAnswers的INNER JOIN，因此您将删除QuestionAnswers中的所有行，而CompleteSurvey中没有相应的行。我认为如果您将它们之间的连接更改为RIGHT OUTER，这将有效。

SELECT  COUNT(DISTINCT dbo.CompleteSurvey.RespondantID) AS [Total Number of Participants], 
        dbo.Answers.Answer, 
        dbo.Questions.Question
FROM    dbo.CompleteSurvey 
        RIGHT OUTER JOIN dbo.QuestionsAnswers 
            ON dbo.CompleteSurvey.QuestionsAnswersID = dbo.QuestionsAnswers.ID 
        INNER JOIN dbo.Questions 
            ON dbo.QuestionsAnswers.QuestionID = dbo.Questions.QuestionID 
        RIGHT OUTER JOIN dbo.Answers 
            ON dbo.QuestionsAnswers.AnswerID = dbo.Answers.AnswerID
GROUP BY dbo.Answers.Answer, dbo.Questions.Question

然而我建议您切换要加入的订单，下面将删除一个OUTER JOIN，它总体上不如INNER JOIN那样好。当使用LEFT JOIN而不是右连接时，它（在我的选项中）也使得查询更容易。

SELECT  COUNT(DISTINCT dbo.CompleteSurvey.RespondantID) AS [Total Number of Participants], 
        dbo.Answers.Answer, 
        dbo.Questions.Question
FROM    dbo.Questions
        INNER JOIN dbo.QuestionAnswers
            ON Questions.QuestionID = QuestionAnswers.QuestionID
        INNER JOIN dbo.Answers
            ON QuestionAnswers.AnswerID = Answers.AnswerID
        LEFT JOIN dbo.CompleteSurvey
            ON QuestionAnswers.QuestionAnswersID = CompleteSurvey.QuestionAnswersID
GROUP BY Answers.Answer, Questions.Question

更新要求

如果我正确理解了这些要求，您只需要加入员工和部门来质疑，以便获得该部门。这可以通过左连接两次来完成，但是我把它移动到子查询除了我喜欢在我可以使用INNER JOIN之外没有其他原因，所以如果有一种方法我可以用更少的OUTER JOIN重新排列查询我会做到这一点：

SELECT  COUNT(DISTINCT CompleteSurvey.RespondantID) AS [Total Number of Participants], 
        Answers.Answer, 
        Questions.Question,
        DepartName
FROM    dbo.Questions
        INNER JOIN dbo.QuestionsAnswers
            ON Questions.QuestionID = QuestionsAnswers.QuestionID
        INNER JOIN dbo.Answers
            ON QuestionsAnswers.AnswerID = Answers.AnswerID
        CROSS JOIN Departments
        LEFT JOIN 
        (   SELECT  OrgCode, QuestionsAnswersID, RespondantID
            FROM    dbo.CompleteSurvey
                    INNER JOIN dbo.Employees
                        ON EmployeeID = RespondantID
        ) CompleteSurvey
            ON QuestionsAnswers.ID = CompleteSurvey.QuestionsAnswersID
            AND Departments.OrgCode = CompleteSurvey.OrgCode
GROUP BY Answers.Answer, Questions.Question, DepartName
ORDER BY Questions.Question, Answers.Answer, DepartName

即使其中一个没有参与者，如何显示所有答案？

1 个答案: