Question

问题在于：

CREATE TABLE #datesX
    (
    [Name] [varchar] (8) NULL
    , [MarriedDate] datetime NULL
    , [HappyScoreX] [int] NULL
    ) 
INSERT INTO #datesX 
    values 
     ('TIM', null, 20),
     ('RAJ', '01 jan 2012', 20),
     ('PAUL', '01 jan 1960', 20)


CREATE TABLE #datesY
    (
    [Name] [varchar] (8) NULL
    , [FirstSprogDate] datetime NULL
    , [HappyScoreY] [int] NULL
    ) 
INSERT INTO #datesY 
    values 
     ('TIM', '01 jan 1995', 20),
     ('RAJ', '20 JUN 2013', 20),
     ('JASE', null, 20),
     ('PAUL', '01 jan 1970', 20)


CREATE TABLE #datesZ
    (
    [Name] [varchar] (8) NULL
    , [FoundGodDate] datetime NULL
    , [HappyScoreZ] [int] NULL
    ) 
INSERT INTO #datesZ 
    values 
     ('TIM', null, 20),
     ('RAJ', null, 20),
     ('JASE', '01 DEC 2012', 20),
     ('PAUL', '01 jan 1970', 20)




SELECT 
        [Name] = COALESCE(x.Name, y.Name, z.Name), 
        x.[MarriedDate],
        y.[FirstSprogDate],
        z.[FoundGodDate],
        [HappyScoreX] = SUM(ISNULL(x.[HappyScoreX],0.0)),
        [HappyScoreY] = SUM(ISNULL(y.[HappyScoreY],0.0)),
        [HappyScoreZ] = SUM(ISNULL(z.[HappyScoreZ],0.0))
FROM 
        #datesX x
        FULL OUTER JOIN #datesY y ON
                x.Name = y.Name 
        FULL OUTER JOIN #datesZ z ON
                x.Name = z.Name 
GROUP BY
        COALESCE(x.Name, y.Name, z.Name), 
        x.[MarriedDate],
        y.[FirstSprogDate],
        z.[FoundGodDate]

我可以理解为什么JASE的记录被重复 - 我如何修改查询以便JASE只有一条记录？

Answer 1

请尝试此连接：

FULL OUTER JOIN #datesY y ON
       x.Name = y.Name 
FULL OUTER JOIN #datesZ z ON
       coalesce(x.Name, y.name) = z.Name

Answer 2

每个名称需要一行。我的建议是首先建立密钥，然后去获取行。

CREATE TABLE #nameKeys
(
  [Name] varchar(8) NOT NULL PRIMARY KEY
)

INSERT INTO #nameKeys ([Name])
SELECT DISTINCT [Name] FROM #datesX WHERE [Name] is not null
UNION
SELECT DISTINCT [Name] FROM #datesYY WHERE [Name] is not null
UNION
SELECT DISTINCT [Name] FROM #datesZ WHERE [Name] is not null


--Then later...

FROM
  #nameKeys n
  LEFT JOIN #datesX x ON n.[Name] = x.[Name]
  LEFT JOIN #datesY y ON n.[Name] = y.[Name]
  LEFT JOIN #datesZ z ON n.[Name] = z.[Name]

Answer 3

您遇到的麻烦是#datesX上有两个FULL OUTER JOINS。由于JASE的#datesX中没有行，因此您可以从Y和Z表中返回行，但是您的上一个Full外部会确定您应该将X.Name与Z.Name匹配。以下代码将为您提供您想要的（我认为|）

SELECT 
        [Name] = COALESCE(x.Name, y.Name, z.Name), 
        x.[MarriedDate],
        y.[FirstSprogDate],
        z.[FoundGodDate],
        [HappyScoreX] = SUM(ISNULL(x.[HappyScoreX],0.0)),
        [HappyScoreY] = SUM(ISNULL(y.[HappyScoreY],0.0)),
        [HappyScoreZ] = SUM(ISNULL(z.[HappyScoreZ],0.0))
FROM 
        #datesX x
        FULL OUTER JOIN #datesY y ON
                x.Name = y.Name 
        FULL OUTER JOIN #datesZ z ON
                z.Name = COALESCE(x.Name, y.Name)
GROUP BY
        COALESCE(x.Name, y.Name, z.Name), 
        x.[MarriedDate],
        y.[FirstSprogDate],
        z.[FoundGodDate]

Answer 4

为了进一步理解David B的答案，使用Common Table Expression：

是有意义的

;WITH NameKeys
AS
(
    SELECT DISTINCT [Name] FROM #datesX WHERE [Name] is not null
    UNION
    SELECT DISTINCT [Name] FROM #datesYY WHERE [Name] is not null
    UNION
    SELECT DISTINCT [Name] FROM #datesZ WHERE [Name] is not null
)
SELECT 
        n.[Name], 
        x.[MarriedDate],
        y.[FirstSprogDate],
        z.[FoundGodDate],
        [HappyScoreX] = SUM(ISNULL(x.[HappyScoreX],0.0)),
        [HappyScoreY] = SUM(ISNULL(y.[HappyScoreY],0.0)),
        [HappyScoreZ] = SUM(ISNULL(z.[HappyScoreZ],0.0))
FROM NameKeys n
LEFT JOIN #datesX x ON n.[Name] = x.[Name]
LEFT JOIN #datesY y ON n.[Name] = y.[Name]
LEFT JOIN #datesZ z ON n.[Name] = z.[Name]

使用FULL OUTER JOIN / COALESCE时重复结果

4 个答案: