Question 1

What is the difference between Star Schema and Snowflake Schema?

Accepted Answer

In a star schema, dimensions are denormalized into one table per dimension, which means fewer joins and faster query performance. It is simpler to understand and is the preferred structure in Power BI. In a snowflake schema, dimensions are normalized into sub-tables, which can save storage but needs more joins and is more complex.

Question 2

What is the difference between a calculated column and a measure in Power BI?

Accepted Answer

A calculated column is computed row-by-row at data refresh time and stored in the model. A measure is calculated on the fly at query time in the current filter context and is not stored as a column. Measures are preferred for most aggregations and report calculations.

Question 3

What is the order of execution of filters in Tableau?

Accepted Answer

Tableau processes filters in this order: Extract filters, then Data source filters, then Context filters, then filters on dimensions, then filters on measures, and finally Table calculation filters.

Question 4

What is the difference between INNER JOIN and LEFT JOIN in SQL?

Accepted Answer

INNER JOIN returns only rows that match in both tables. LEFT JOIN returns all rows from the left table and matching rows from the right table; when there is no match, right-side columns are NULL.

Question 5

What is DAX in Power BI?

Accepted Answer

DAX (Data Analysis Expressions) is Power BI's formula language, used for calculated columns, measures, and calculated tables. Common function families include aggregation (SUM, AVERAGE), filter context (CALCULATE, FILTER, ALL), time intelligence (TOTALYTD, SAMEPERIODLASTYEAR), and relationship functions such as RELATED.

Question 6

Is CrackAnalytics free?

Accepted Answer

Yes. CrackAnalytics by Mahendra Singh is a free data analyst interview preparation course with 450+ real interview questions and answers covering SQL, Power BI, Tableau, Excel, Data Science and AI, plus aptitude tests and a resource library.

CrackAnalytics Blog