1. Treatise on TREATAS()
Alex Whiteside
08/15/19

2. Data Lineage
DAX preserves the relationships of references to columns and their values* in the data model
Renaming a column does not disrupt data lineage

3. Data Lineage
DAX preserves the relationships of references to columns and their values in the data model
…*but not expressions

4. TREATAS() TREATAS() Introduced in PBI Desktop February 2017
TREATAS(table_expression, <column>[, <column>[, <column>[,…]]]} )
Applies the result of a table expression as filters to columns from an unrelated table.
“treat X as a filter for Y”

5. Performance Ranking
TREATAS() is less efficient than using a physical relationship to propagate a filter (including leveraging an inactive relationship with USERELATIONSHIP()) , but more efficient than creating a virtual relationship with other functions
source: sqlbi “Propagating filters using TREATAS in DAX”

6. Common Scenarios
Surrogate for relationships that cannot be created due to…
filtering ambiguity
C.f. leveraging an inactive relationship with USERELATIONSHIP()
constraints on changing the data model (e.g. using Live Connection)

7. Common Scenarios
Filtering tables of differing granularities e.g. budget/forecast vs actuals

8. Common Scenarios
Filtering a table with a table expression