DAX Calculated Column with "variable tables" as variables.

Hi JavierLopezFALP 

The variable table is the source of the error, since IF must always return a scalar value.

In the below expression, the 2nd and 3rd arguments are table rather than scalar values:

var table = if(countrows(table2) < 1, table1, table2)

One way around this is to rewrite as follows:

column =
--[state] can adopt values 1 to 5, and there are blank values. 
VAR table1 = FILTER ( RELATEDTABLE ( table2 ), NOT ( ISBLANK ( [state] ) ) )
VAR table2 = FILTER ( RELATEDTABLE ( table2 ), [state] IN { 1, 2 } )
VAR selectTable1 = COUNTROWS ( table2 ) < 1
VAR table =
    UNION ( FILTER ( table1, selectTable1 ), FILTER ( table2, NOT selectTable1 ) )
...

Does this work as intended?