Top Power BI Interview Questions with Answers:
1️⃣ What are custom visuals in Power BI? 🎨
Custom visuals are user-created or third-party visuals beyond the default ones in Power BI (e.g., Sankey charts, heat maps). They can be downloaded from Microsoft AppSource or imported via .pbiviz files to meet specific business visualization needs.
2️⃣ How do you optimize Power BI performance? ⚡
– Use star schema for modeling
– Remove unused columns
– Reduce cardinality
– Prefer Import mode over DirectQuery (if possible)
– Use variables in DAX to avoid repeated calculations
– Disable auto date/time in load options
– Avoid bi-directional relationships unless necessary
3️⃣ What is the difference between ALL and ALLEXCEPT in DAX? ↔️
– ALL() removes filters from all columns or a table.
– ALLEXCEPT() removes filters from all columns except the specified ones.
Example:
CALCULATE(SUM(Sales), ALL(Region))
— Ignores Region filter
CALCULATE(SUM(Sales), ALLEXCEPT(Sales, Product))
— Ignores all filters except Product
4️⃣ What is the CALCULATE function in DAX? 🧮
CALCULATE() modifies the context of a calculation by applying filters. It’s used to create dynamic measures.
Example:
Sales_North = CALCULATE(SUM(Sales[Amount]), Region = “North”)
5️⃣ What is the difference between SUMX and SUM? ➕
– SUM() adds up a single column.
– SUMX() adds up the result of a row-wise expression.
Example:
SUM(Sales[Revenue])
SUMX(Sales, Sales[Quantity] * Sales[Price])
6️⃣ How do you handle null or blank values in Power BI? 🚫
Use DAX functions:
– IF(ISBLANK([Column]), “N/A”, [Column])
– COALESCE([Column], 0)
You can also filter or replace blanks using Power Query.
7️⃣ What is the RELATED function in DAX? 🔗
RELATED() fetches values from a related table based on relationships.
Example:
RELATED(Product[Category])
— Gets category name from related Product table
8️⃣ What is a star schema vs snowflake schema? ⭐❄️
– Star schema: Central fact table with denormalized dimension tables.
– Snowflake schema: Dimension tables are normalized (broken into sub-tables).
Star schema is preferred in Power BI for simplicity and performance.
9️⃣ What is Power BI Embedded? 🌐
Power BI Embedded is a Microsoft Azure service that allows developers to embed interactive Power BI visuals and reports into custom applications (web/apps) using APIs and SDKs.
🔟 What are KPIs and how do you create them? 🎯
KPIs (Key Performance Indicators) are metrics that track performance against goals. In Power BI, you can create KPIs using measures and visuals like KPI cards or conditional formatting based on thresholds.
Example: Sales vs Target with colored indicators.
💬 Part-4 Soon
