Power BI interview questions

A calculated column is computed per row at refresh and stored. A measure is computed at query time in the current filter context.

The set of filters applied to a calculation from slicers, rows, columns and CALCULATE.

The current row during iteration, in calculated columns or iterators like SUMX.

It evaluates an expression in a modified filter context. It is the most important DAX function.

Sales West = CALCULATE([Total Sales], Region[Name] = "West")

When CALCULATE turns the current row context into an equivalent filter context.

SUM adds a column. SUMX iterates rows and sums an expression per row, like quantity times price.

It gives simpler DAX, correct filtering and better performance than flat or snowflaked tables.

Time intelligence functions need a continuous date table marked as a date table.

Import loads data into the model and is fastest. DirectQuery queries the source live, for very large or real-time data, but is slower.

Power Query pushing transformations back to the source as SQL, which is much faster.

Define roles with DAX filters in Desktop, then assign users or groups to roles in the Service.

Single direction filters from one side to many. Bidirectional can cause ambiguity and slow models, so use it carefully.

Compare current sales to SAMEPERIODLASTYEAR.

YoY % = DIVIDE([Sales] - CALCULATE([Sales], SAMEPERIODLASTYEAR('Date'[Date])), CALCULATE([Sales], SAMEPERIODLASTYEAR('Date'[Date])))

DIVIDE handles division by zero safely.

VAR stores a value once, making measures faster and easier to read.

Reduce columns and cardinality, use measures not calculated columns, avoid bidirectional filters and check with Performance Analyzer and DAX Studio.

Software that lets the Power BI Service refresh data from on-premises sources.

Bookmarks save a report view state. Drill-through lets users jump to a detail page filtered by what they clicked.

A workspace is where you build and collaborate. An app is the polished package you publish to report viewers.

The Microsoft Power BI Data Analyst certification exam.