Question

Here is the problem:

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]

I can sort of see why the record for JASE is being duplicated – how do I amend the query so that JASE only has one record ?

Answer 1

Try this join instead:

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