Power Bi Dax Fundamentals is one of the core study topics in our Technology catalog. This page gathers the essentials: what the topic covers, the key concepts and
terminology, worked examples and exam-style questions — everything also available as 214 companion flashcards for spaced-repetition practice.
Main questions this page answers:
- What is a DAX measure?
- How does filter context work in DAX?
- What does the CALCULATE function do?
- What is the syntax for CALCULATE?
- What is the difference between CALCULATE and CALCULATETABLE?
- What is time intelligence in DAX?
- Why must a date table be marked in Power BI?
- What does TOTALYTD return?
What is a DAX measure?
A calculated formula created using DAX that is evaluated at query time based on filter context. Measures return dynamic values depending on the filters applied in the report, unlike calculated columns which are computed at refresh time.
What is a calculated column?
A calculated column is a DAX expression added to a table that evaluates row by row at refresh time. It is stored in the model, consumes memory, and is not affected by user filter context.
What is the difference between VALUES and DISTINCT in DAX?
VALUES returns a single column of distinct values while preserving blank rows associated with the column. DISTINCT also returns unique values but does not include the blank row. Both are often used in slicers and lookup logic.
What is a Dimension table?
A Dimension table contains descriptive attributes used to filter, group, or label data (e.g., product, customer, date). In a star schema, dimensions surround the fact table and support analysis.
What is a measure in Power BI?
A measure is a DAX calculation stored in the data model that is computed at query time based on filter context. Measures are calculated on demand and are typically used for aggregations, ratios, time intelligence, and KPI values in visuals.
What is a Dual storage mode in Power BI?
Dual storage mode lets a table act as Import in some queries and DirectQuery in others. The engine chooses the appropriate mode based on the query so dimension tables can be cached while fact tables query source directly.
What does the TREATAS function do in DAX?
TREATAS applies the result of a table expression as filters to columns from unrelated tables. It is used to link disconnected or virtual tables by creating virtual relationships, often for parameter-driven or dynamic segmentation scenarios.
What is a slicer synchronization limitation in Power BI?
Slicer sync allows a slicer on one page to be shared across other pages. It does not synchronize selections across pages automatically; enabling sync only makes the slicer appear on each synced page with its own state unless controlled separately.
What does the CROSSJOIN function do?
CROSSJOIN returns a Cartesian product of two tables, combining every row from the first table with every row from the second. Useful for generating parameter combinations.
What is the ISCROSSFILTERED function?
ISCROSSFILTERED returns TRUE when a column is affected by filters propagated through relationships from other tables. It does not require a direct filter on the column itself, only an indirect one through the model.