Power Pivot Principles: The A to Z of DAX Functions – FIRSTNONBLANKVALUE

In our long-established Power Pivot Principles articles, we continue our series on the A to Z of Data Analysis eXpression (DAX) functions.  This week, we look at FIRSTNONBLANKVALUE. 

The FIRSTNONBLANKVALUE function

The FIRSTNONBLANKVALUE function is one of the time intelligence functions which returns the first value in the column that the expression has a non-blank value.  It has the following syntax:

• column: this is required which is a column expression.  The column argument may be either of the following:
  • a reference to any column
  • a table with a single column
• expression: this is also required, and is an expression evaluated for each value of column.

It should be further noted that:

• the difference between the FIRSTNONBLANK function and the FIRSTNONBLANKVALUE function is that the column argument of FIRSTNONBLANKVALUE 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.

Since the FIRSTNONBLANKVALUE function is a time intelligence function, it should be noted that:

• all dates need to be present for the years required.  All the days in this span, from January 1 to December 31, must be included in the Date table.  The date table must include all dates from commencement to the last day of a fiscal year if the report solely refers to fiscal years
• a column with a DateTime or Date data type and unique values is required.  Typically, this column is known as Date.  Although it is common practice, this is not necessary when defining associations with other tables.  However, the ‘mark as Date Table’ feature should relate to the Date column, which must have distinct values
• the Date table must be designated as a date table in the model in case the relationship between the Date table and any other table is not dependent on the Date.

Let’s consider the following example, where we have the following TB_Sales table in Power BI:

We will write a measure to get the first non-blank value for a selected date:

If we drag and drop this measure and then create a slicer for selecting a date range, we may obtain something similar to the following:

It will show the first non-blank value for the selected date range.

Come back next week for our next post on Power Pivot in the Blog section.  In the meantime, please remember we have training in Power Pivot which you can find out more about here.  If you wish to catch up on past articles in the meantime, you can find all of our Past Power Pivot blogs here.