Select from two different tables and group by dates
;WITH First_table 
AS (SELECT '2015-03-08' AS [Date],'Diag1' AS Diagnostics, 2932 AS ID
    UNION ALL SELECT '2015-03-09','Diag2', 2932
    )
,Second_table
AS (SELECT '2015-03-09' AS [Date], 'Eval1' AS Evaluation ,2932 AS ID
    UNION ALL SELECT '2015-03-09','Eval2',2932
    UNION ALL SELECT '2015-03-10' ,'Eval3' , 2932)


SELECT
    KT.[Date] AS [Date]
    ,FT.Diagnostics AS [Diagnostics]
    ,STUFF(ST.Evaluation,1,1,'') AS [Evaluation]
FROM
    (
        SELECT [Date] ,[ID]
        FROM First_table
        --GROUP BY [Date] ,[ID]

        UNION 

        SELECT [Date] ,[ID]
        FROM Second_table
        --GROUP BY [Date] ,[ID]
    ) AS KT  --keyTAble
    LEFT JOIN First_table AS FT
        ON kt.[Date] = FT.[Date]
        AND kt.[ID]= FT.[ID]
    OUTER APPLY
        (
            SELECT 
                ',' + Evaluation
            FROM Second_table AS ST
            WHERE 
                KT.[DATE] =ST.[Date]
                AND kT.[ID]= ST.[ID]
            FOR XML PATH('')
        )ST(Evaluation)