如何從連接到左外連接的表中獲取計數？

Question

我有三張桌子。的測試的表（AdminTest）的屬於用戶（UserTest）和問題屬於每個用戶測試的一個表（UserTestQuestion）測試的表：

AdminTest

UserTest

CREATE TABLE [dbo].[UserTest] (
    [UserTestId] INT  IDENTITY (1, 1) NOT NULL, 
    [AdminTestId] INT  NOT NULL, 
    [UserId]  INT  NOT NULL 
    CONSTRAINT [PK_UT] PRIMARY KEY CLUSTERED ([UserTestId] ASC)); 

UserTestQuestion

CREATE TABLE [dbo].[UserTestQuestion] (
    [UserTestQuestionId] INT    IDENTITY (1, 1) NOT NULL, 
    [UserTestId]   INT    NOT NULL, 
    [Answered]   BIT    DEFAULT ((0)) NOT NULL 
    CONSTRAINT [PK_UQ] PRIMARY KEY CLUSTERED ([UserTestQuestionId] ASC) 
); 

• 的AdminTest可能會或可能不會有UserTest
• 一個UserTest總會有UserTestQuestions

我創造了這個SQL擺脫AdminTest和UserTest數據：

SELECT userTest.StartedDate, 
     temp.AdminTestId 
     -- AnsweredCount 
     -- I want to get a count of the number of rows 
     -- from the table UserTestQuestions that have 
     -- the column 'Answered' set to 1 here.    
FROM 
(SELECT AdminTest.AdminTestId 
    FROM AdminTest 
    JOIN AdminTestQuestion ON AdminTest.AdminTestId = AdminTestQuestion.AdminTestId  
GROUP BY 
    AdminTest.AdminTestId 
) temp 
LEFT OUTER JOIN UserTest ON temp.AdminTestId = UserTest.AdminTestId 
-- I want the above join to only join those UserTest tables that 
-- have a value of UserId set to for example 25 

但現在我堅持有兩件事我需要幫助。

• 我需要能夠顯示只屬於定UserID
• 我需要在回答設爲1

的UserTests報告的行數的UserTests有人可以給我建議如何將這個功能添加到我的SQL？

這裏是什麼，我需要一個例子：

AdminTestId UserTestStartedData AnsweredCount 

1    1/1/2001    25 
2    2/2/2002    10 
3     
4    4/4/2004    10 

Answer 1

加入UserTestQuestion表並使用Conditional Aggregate只有當answered = 1

SELECT userTest.StartedDate, 
     temp.AdminTestId, 
     Count(CASE 
       WHEN UT.answered = 1 THEN 1 
      END) cnt 
FROM (SELECT AdminTest.AdminTestId 
     FROM AdminTest 
       JOIN AdminTestQuestion 
       ON AdminTest.AdminTestId = AdminTestQuestion.AdminTestId 
     GROUP BY AdminTest.AdminTestId) temp 
     INNER JOIN UserTest 
        ON temp.AdminTestId = UserTest.AdminTestId 
     INNER JOIN [UserTestQuestion] UT 
       ON UserTest.UserTestId = UT.UserTest 
     Where UserTest.UserTestId = 25 

此外，如果你想加入到只參加那些UserTest表來算那 的值爲UserId=25則left join將被轉換爲Inner join

更新：

SELECT A.StartedDate, 
     temp.AdminTestId, 
     Count(CASE 
       WHEN A.answered = 1 THEN 1 
      END) cnt 
FROM (SELECT AdminTest.AdminTestId 
     FROM AdminTest 
       JOIN AdminTestQuestion 
       ON AdminTest.AdminTestId = AdminTestQuestion.AdminTestId 
     GROUP BY AdminTest.AdminTestId) temp 
     LEFT OUTER JOIN (SELECT userTest.StartedDate, 
           UT.answered, 
           UserTest.AdminTestId 
         FROM UserTest 
           INNER JOIN [UserTestQuestion] UT 
             ON UserTest.UserTestId = UT.UserTest 
         WHERE UserTest.UserTestId = 25) A 
        ON temp.AdminTestId = A.AdminTestId 
Group by A.StartedDate,temp.AdminTestId