PART1: Tutorial with example
In today’s DAX Fridays! video we will go through the DAX function UNION. UNION function will append two tables using DAX language.
Let me start by saying: “you shouldn’t do it in DAX”, but if you still have to do it, in this video I will show you how to unpivot tables with DAX. I will then unpivot them using Power Query so you can see the difference, and how Power Query can be faster and more efficient for cleaning data.
Download example file:
Link to Power BI file: here.
The two tables must have the same number of columns.
Columns are combined by position in their respective tables.
The column names in the return table will match the column names in table_expression1.
Duplicate rows are retained.
The returned table has lineage where possible. For example, if the first column of each table_expression has lineage to the same base column C1 in the model, the first column in the UNION result will have lineage to C1. However, if combined columns have lineage to different base columns, or if there is an extension column, the resulting column in UNION will have no lineage.
When data types differ, the resulting data type is determined based on the rules for data type coercion.
The returned table will not contain columns from related tables.