Question

I am trying to do something similar to
How can I improve this SQL query?

However, in there logic
Essentially I have a list of IDs that could have multiple values associated with them, the values being Yes, No, or some other string. For ID x, if any of the values are a Yes, x should be Yes, if they are all No, it should be No, if they contain any other values but yes and no, display that value. I only want to return 1 row per ID, no duplicates.

but in my logic if all values are yes, then display yes, if all values are no then display no, if it is a mix of yes,no or anything else display mix

DECLARE @tempTable table ( ID int, Val varchar(1) )

    INSERT INTO @tempTable ( ID, Val ) VALUES ( 10, 'Y')
    INSERT INTO @tempTable ( ID, Val ) VALUES ( 11, 'N')
    INSERT INTO @tempTable ( ID, Val ) VALUES ( 11, 'N')
    INSERT INTO @tempTable ( ID, Val ) VALUES ( 12, 'Y')
    INSERT INTO @tempTable ( ID, Val ) VALUES ( 12, 'Y')
    INSERT INTO @tempTable ( ID, Val ) VALUES ( 12, 'Y')
    INSERT INTO @tempTable ( ID, Val ) VALUES ( 13, 'N')
    INSERT INTO @tempTable ( ID, Val ) VALUES ( 14, 'Y')
    INSERT INTO @tempTable ( ID, Val ) VALUES ( 14, 'N')
    INSERT INTO @tempTable ( ID, Val ) VALUES ( 15, 'Y')
    INSERT INTO @tempTable ( ID, Val ) VALUES ( 16, 'Y')
    INSERT INTO @tempTable ( ID, Val ) VALUES ( 17, 'F')
    INSERT INTO @tempTable ( ID, Val ) VALUES ( 18, 'P')


    SELECT DISTINCT t.ID, COALESCE(t2.Val, t3.Val, t4.Val)
    FROM @tempTable t
    LEFT JOIN
    (
        SELECT ID, Val
        FROM @tempTable
        WHERE Val = 'Y'
    ) t2 ON t.ID = t2.ID
    LEFT JOIN
    (
        SELECT 
        ID, Val FROM @tempTable
        WHERE Val = 'N'
    ) t3 ON t.ID = t3.ID
    LEFT JOIN
    (
        SELECT ID, Val
        FROM @tempTable
        WHERE Val <> 'Y' AND Val <> 'N'
    ) t4 ON t.ID = t4.ID

Update dbo.households
SET dbo.households.code = #TempTable.code
FROM #TempTable
WHERE dbo.households.id = #TempTable.id 

Answer 1

SELECT  ID ,
        CASE WHEN MAX(Val) = MIN(Val)
                  AND MAX(Val) IN ( 'N', 'Y' ) THEN MAX(Val)
             ELSE 'M'
        END
FROM    @tempTable
GROUP BY ID

Or a version that returns Y if any exist rather than if all are Y

SELECT  ID ,
        ISNULL(MAX(CASE WHEN Val = 'Y' THEN 'Y' END), 
               CASE WHEN MAX(Val) = MIN(Val) THEN MAX(Val)
                              ELSE 'M'
                         END)
FROM    @tempTable
GROUP BY ID

Or a final version that takes literally the “if they contain any other values but yes and no, display that value.” statement.

SELECT  ID ,
        ISNULL(MAX(CASE WHEN Val = 'Y' THEN 'Y'END), 
               ISNULL(MAX(CASE WHEN Val NOT IN ( 'N', 'Y' ) THEN Val END), 
                      MAX(Val)))
FROM    @tempTable
GROUP BY ID