FIRSTNONBLANKVALUE

Evaluates an expression filtered by the sorted values of a column and returns the first value of the expression that is not blank.

Syntax

FIRSTNONBLANKVALUE(<column>, <expression>)

Term	Definition
column	A column or an expression that returns a single-column table.
expression	An expression evaluated for each value of <column>.

The first non-blank value of <expression> corresponding to the sorted values of <column>.

The column argument can be any of the following:
- A reference to any column.
- A table with a single column.
This function is different from FIRSTNONBLANK in that the <column> is added to the filter context for the evaluation of <expression>.
This function is not supported for use in DirectQuery mode when used in calculated columns or row-level security (RLS) rules.

The following DAX query,

EVALUATE 
SUMMARIZECOLUMNS(
  DimProduct[Class],
  "FNBV",
  FIRSTNONBLANKVALUE(
    DimDate[Date],
    SUM(FactInternetSales[SalesAmount])
   )
)

Returns,