即使沒有參與者在其中之一，如何顯示所有答案？

Question

我有以下的數據庫設計：

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 

每個問題都有不同的多種選擇。大多數問題具有相同的選擇，如（同意，不同意）。我想編寫一個查詢，顯示所有選擇的問題以及每個選擇中的參與者數量，即使它是零。 我寫了查詢，它顯示了問題的所有答案，即使沒有人選擇其中一個答案，但查詢在除了沒有參與者的答案之外的問題列中顯示NULL，我不知道爲什麼。請幫忙嗎？

我的查詢：

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 

UPDATE：

查詢應顯示在所有的答案的問題，各部門的參與者的數量，所以該怎麼做？

我的更新查詢：

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 

但它的問題不顯示的部門。它應該顯示每個問題中每個部門的參與者數量及其所有答案，即使沒有參與者提供答案之一。

Answer 1

QuestionAnswers是獲得答案所需的表，而是因爲你使用的是INNER JOIN從CompleteSurvey到QuestionAnswers你消除在CompleteSurvey沒有相應的行QuestionAnswers所有行。我認爲如果您將它們之間的連接更改爲RIGHT OUTER，這將起作用。

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 

然而我建議切換你是加盟一輪的順序，以下將消除一個OUTER JOIN，這在整體上不執行以及內部連接。它也（在我的選擇中）使得在使用LEFT JOIN而不是右連接時更容易閱讀查詢。

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 

---

更新的要求

如果我理解正確的要求，你只需要加入的員工和部門對問題答案來獲取部門。這可以通過左連接兩次完成，但是我已經將它移到子查詢中，除了我喜歡在所需的位置使用INNER JOIN之外，沒有其他原因，所以如果有方法我可以重新排列具有較少OUTER JOIN的查詢，我會做它：

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