DAX conditional sum

问题

How to construct a DAX measure which returns sum of either A or B. The logic is take B if A is empty. So expected results looks like this:

+---+---+----------+
| A | B | Expected |
+---+---+----------+
| 1 |   |        1 |
| 1 |   |        1 |
|   | 2 |        2 |
| 1 | 2 |        1 |
|   | 2 |        2 |
+---+---+----------+
| 3 | 6 |        7 |
+---+---+----------+

When I use measure:

Measure = IF(ISBLANK([SUM(tab[A])]), SUM(tab[B]), SUM(tab[A]))

I get 3 for total which is logical but not what I expect.

回答1:

I'd recommend using a SUMX iterator in this case.

Measure = SUMX ( tab, IF ( ISBLANK ( tab[A] ), tab[B], tab[A] ) )

You might be able to do the following as well:

Measure = 
    CALCULATE ( SUM ( tab[A] ) ) +
    CALCULATE ( SUM ( tab[B] ),
        FILTER ( tab, ISBLANK( tab[A] ) )
    ) 

来源：https://stackoverflow.com/questions/57693531/dax-conditional-sum