Running Total and Null Values

Hi there.

You are getting "strange" results because you are not following Best Practices of dimensional design - easy as that.

If you run this in DaxStudio:

DEFINE
    MEASURE Conccentrator_Final[MTD2] =
        CALCULATE (
            [BTZ RMO],
            DATESMTD( 'Calendar'[Date] ),
            Conccentrator_Final[Feed Oz's_2] > 0
        )
EVALUATE
CALCULATETABLE (
    ADDCOLUMNS (
        VALUES ( 'Calendar'[Date] ),
        "RMO", ROUND ( [BTZ RMO], 0 ),
        "MTD", ROUND ( [BTZ RMO MTD], 0 ),
        "MTD2", Round( [MTD2], 0 )
    ),
    'Calendar'[YYYY-MM] = "2020-02"
)

you'll see that [MTD2] gives you the correct answer. The reason being, [MTD2] uses Calendar to do any time-intel calculations. Such calculations do work correctly ONLY in case you are applying the functions to a proper Date table in the model. Any other column and you're out of luck.

You should strictly follow these golden rules if you want to stay on the safe side:

1. Slicing is only ever done through dimensions.

2. Fact tables' columns are all hidden without exceptions. Only measures can be visible.

3. Time-intel is applied only to proper Date tables.

4. The design must be either a star or a flake schema. Any deviation from this and you're asking for troubles.

6. Bi-directional filtering is used ONLY when strictly necessary. 99% of filtering is one-way only.

Best

D