计数行基于存在的条件

Question

我已经研究演示如何添加条件使用CASE语句计数语句，但我找不到怎么做，我需要一个例子很多问题＃1。假设我有以下表格：

CREATE TABLE [Project](
    [ProjectId] [int] NOT NULL, 
    [ProjectName] [nvarchar](100) NOT NULL 
) 
GO 

CREATE TABLE [ProjectTask](
    [ProjectTaskId] [int] NOT NULL, 
    [ProjectId] [int] NOT NULL, 
    [TaskName] [nvarchar](100) NOT NULL 
) 
GO 

CREATE TABLE [ProjectTaskOwner](
    [ProjectTaskId] [int] NOT NULL, 
    [UserId] [int] NOT NULL 
) 
GO 

CREATE TABLE [ProjectTaskEntity](
    [ProjectTaskId] [int] NOT NULL, 
    [EntityId] [int] NOT NULL, 
    [AssignedUserId] [int] 
) 
GO 

INSERT Project (ProjectId, ProjectName) VALUES (1, 'Test Project') 
INSERT ProjectTask (ProjectTaskId, ProjectId, TaskName) VALUES(1, 1, 'Task1') 
INSERT ProjectTask (ProjectTaskId, ProjectId, TaskName) VALUES(2, 1, 'Task2') 
INSERT ProjectTaskOwner (ProjectTaskId, UserId) VALUES (1, 1) 
INSERT ProjectTaskOwner (ProjectTaskId, UserId) VALUES (1, 2) 
INSERT ProjectTaskOwner (ProjectTaskId, UserId) VALUES (1, 3) 
INSERT ProjectTaskEntity (ProjectTaskId, EntityId, AssignedUserId) VALUES (1, 1, 1) 
INSERT ProjectTaskEntity (ProjectTaskId, EntityId, AssignedUserId) VALUES (1, 2, 2) 
INSERT ProjectTaskEntity (ProjectTaskId, EntityId, AssignedUserId) VALUES (1, 3, 3) 
INSERT ProjectTaskEntity (ProjectTaskId, EntityId, AssignedUserId) VALUES (1, 4, 256) 

我想要做的就是让每个项目任务分配给我，并分配给其他任务所有者的实体的数量。因此，对于上面的测试数据，鉴于1的用户ID和1项目ID我想到：

| TaskId | AssignedToMe | AssignedToOthers | 
| 1 |  1  |  2   | 
| 2 |  0  |  0   | 

所以这是我到目前为止有：

DECLARE @userId INT = 1 
SELECT 
    pt.ProjectId, 
    pt.ProjectTaskId, 
    COUNT(CASE WHEN pte.AssignedUserId = @userId THEN 1 ELSE NULL END) AS AssignedTo 
FROM ProjectTask pt 
INNER JOIN Project p 
    ON p.ProjectId = pt.ProjectId 
LEFT JOIN ProjectTaskEntity pte 
    ON pte.ProjectTaskId = pt.ProjectTaskId 
WHERE p.ProjectId = 1 
GROUP BY pt.ProjectId, pt.ProjectTaskId 

分配给我的是容易。问题是我不知道如何去做别人，因为别人不只是我不是。任何人都不在此任务的ProjectTaskOwner表中。任何人有任何想法如何实现这一目标？

Answer 1

这里是解决我的问题的实际查询。有几个职位，帮我找到这个所以感谢大家对你的答案：

DECLARE @userId INT = 1 
SELECT 
    pt.ProjectId, 
    pt.ProjectTaskId, 
    COUNT(CASE WHEN pte.AssignedUserId = @userId THEN 1 ELSE NULL END) AS AssignedTo, 
    COUNT(CASE WHEN eao.OtherUser IS NULL THEN NULL ELSE 1 END) AS AssignedToOther 
FROM ProjectTask pt 
LEFT JOIN ProjectTaskEntity pte 
    ON pte.ProjectTaskId = pt.ProjectTaskId 
LEFT JOIN (
    SELECT sPto.ProjectTaskId, sPto.UserId as OtherUser 
    FROM ProjectTaskOwner sPto 
    WHERE sPto.UserId <> @userId 
) eao 
    ON pt.ProjectTaskId = eao.ProjectTaskId AND pte.AssignedUserId = eao.OtherUser 
WHERE pt.ProjectId = 1 
GROUP BY pt.ProjectId, pt.ProjectTaskId 

Answer 2

这就像做相反

DECLARE @userId INT = 1 
SELECT 
    pt.ProjectId, 
    pt.ProjectTaskId, 
    COUNT(CASE WHEN pte.AssignedUserId = @userId THEN 1 ELSE NULL END) AS AssignedToMe, 
    COUNT(CASE WHEN pte.AssignedUserId = @userId THEN null ELSE 0 END) AS AssignedToOthers 

FROM ProjectTask pt 
INNER JOIN Project p 
    ON p.ProjectId = pt.ProjectId 
LEFT JOIN ProjectTaskEntity pte 
    ON pte.ProjectTaskId = pt.ProjectTaskId 
WHERE p.ProjectId = 1 
GROUP BY pt.ProjectId, pt.ProjectTaskId 

Answer 3

我不明白为什么你需要项目表这么简单。我会写这样的：

SELECT pt.ProjectId, pt.ProjectTaskId, 
     SUM(CASE WHEN pte.AssignedUserId = @userId THEN 1 ELSE 0 END) AS AssignedToMe, 
     SUM(CASE WHEN pto.UserId IS NULL THEN 1 ELSE 0 END) AS AssignedToOthers 
FROM ProjectTask pt LEFT JOIN 
    ProjectTaskEntity pte 
    ON pte.ProjectTaskId = pt.ProjectTaskId LEFT JOIN 
    ProjectTaskOwner pto 
    ON pto.ProjectTaskId = pt.ProjectTaskId AND 
     pto.UserId = pte.AssignedUserId 
WHERE pt.ProjectId = 1 
GROUP BY pt.ProjectId, pt.ProjectTaskId; 

我SUM()取代COUNT()。作为一个优先事项，在这种情况下，我更喜欢SUM()。

Answer 4

使用SUM代替COUNT：

DECLARE @userId INT = 1 
SELECT pt.ProjectTaskId, 
    ISNULL(SUM(CASE WHEN pte.AssignedUserId = @userId THEN 1 END),0) AS AssignedToMe, 
    ISNULL(SUM(CASE WHEN pte.AssignedUserId <> @userId THEN 1 END),0) AS AssignedToOthers 
FROM ProjectTask pt 
INNER JOIN Project p ON p.ProjectId = pt.ProjectId 
LEFT JOIN ProjectTaskEntity pte ON pte.ProjectTaskId = pt.ProjectTaskId 
WHERE p.ProjectId = 1 
GROUP BY pt.ProjectTaskId 

与您所提供的数据，这将导致：

ProjectTaskId AssignedToMe AssignedToOthers 
1    1    3 
2    0    0 

参见导致SQL Fiddle。

Answer 5

我认为这解决了这个问题。 你会看别人的不是你，任何人都不能在ProjectTaskOwner表完成这个任务。

DECLARE @userId INT = 1 
SELECT 
    pt.ProjectId, 
    pt.ProjectTaskId, 
    COUNT(CASE WHEN pte.AssignedUserId = @userId THEN 1 ELSE NULL END) AS AssignedTo, 
    COUNT(CASE WHEN pte.AssignedUserId != @userId AND pte.AssignedUserId != pto.UserId THEN 1 ELSE NULL END) AS AssignedTo 
FROM ProjectTask pt 
INNER JOIN Project p 
    ON p.ProjectId = pt.ProjectId 
LEFT JOIN ProjectTaskEntity pte 
    ON pte.ProjectTaskId = pt.ProjectTaskId 
LEFT JOIN ProjectTaskOwner pto 
    on pto.ProjectTaskId = pt.ProjectTaskId 
WHERE p.ProjectId = 1 
GROUP BY pt.ProjectId, pt.ProjectTaskId 

Answer 6

DECLARE @userId INT = 1 
SELECT 
    pt.ProjectId, 
    pt.ProjectTaskId, 
    ISNULL(SUM(CASE WHEN pte.AssignedUserId = @userId THEN 1 END),0) AS AssignedToMe, 
    ISNULL(SUM(CASE WHEN pte.AssignedUserId <> @userId THEN 1 END),0) AS AssignedToOthers 
FROM ProjectTask pt 
INNER JOIN Project p 
    ON p.ProjectId = pt.ProjectId 
LEFT JOIN ProjectTaskOwner pto 
    ON pto.ProjectTaskId = pt.ProjectTaskId 
LEFT JOIN ProjectTaskEntity pte 
    ON pte.ProjectTaskId = pt.ProjectTaskId and 
    pte.AssignedUserId = pto.UserId 
WHERE p.ProjectId = 1 
GROUP BY pt.ProjectId, pt.ProjectTaskId 

http://www.sqlfiddle.com/#!6/58f1e4/28