Microsoft Power BI Power BI Data Modeling 2

Question 1

In Power BI, what is a 'calculated column' and when is it evaluated?

Accepted Answer

A DAX column added to a table, evaluated at data refresh/load time

Answer

A calculated column is defined using DAX and is computed and stored in the model at data refresh or load time.

Question 2

What is a 'snowflake schema' in Power BI?

Accepted Answer

A star schema where dimension tables are further normalized into sub-tables

Answer

A snowflake schema extends a star schema by normalizing dimension tables into multiple related sub-dimension tables.

Question 3

When should you use a 'measure' instead of a 'calculated column' in Power BI?

Accepted Answer

When the calculation aggregates data dynamically based on filter context

Answer

Measures are best for dynamic aggregations that change based on the current filter or row context at query time.

Question 4

What happens to model performance if you have too many calculated columns in a large Power BI dataset?

Accepted Answer

Dataset file size increases and refresh times slow down

Answer

Each calculated column adds to the in-memory storage of the model, increasing file size and potentially slowing refresh times.

Question 5

What is the purpose of a 'date table' in a Power BI data model?

Accepted Answer

To enable time intelligence DAX functions to work correctly

Answer

A properly configured date table is required for DAX time intelligence functions like TOTALYTD and SAMEPERIODLASTYEAR to work correctly.

Microsoft Power BI Practice Test