filter when there is no value

Hi, Anonymous 

Based on your description, I created data to reproduce your scenario. The pbix file is attached in the end.

Table1:

Table2:

Calendar(a calculated table):

Calendar = 
ADDCOLUMNS(
    CALENDARAUTO(),
    "YYYY-MM",
    FORMAT([Date],"yyyy-MM")
)

Relationship:

You may create a measure as below.

Result = 
var tab = 
ADDCOLUMNS(
    Table1,
    "Re",
    var caseid = [CaseID]
    var s = [Start Prod]
    var e = [End Prod]
    var t1 = 
    CALCULATETABLE(
        DISTINCT('Calendar'[YYYY-MM]),
        FILTER(
            ALL('Calendar'),
            [Date]>=s&&
            [Date]<=e
        )
    )
    var t2 = 
    SELECTCOLUMNS(
            ADDCOLUMNS(
                FILTER(
                   ALL(Table2),
                   [CaseID]=caseid
                ),
                "YM",
                FORMAT([Date],"yyyy-MM")
            ),
            "YM",
            [YM]
    )
    return
    CONCATENATEX(
        FILTER(
            t1,
            NOT([YYYY-MM] in t2)
        ),
        [YYYY-MM],
        ","
    )
)
return
CONCATENATEX(
    tab,
    [Re],
    ","
)

Result:

Best Regards

Allan

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