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Wednesday 27 December 2023

What could be the difference between Distinct() and Values() in DAX ? Power BI interview questions and answers167

 What could be the difference between Distinct() and Values() in DAX ?


While both Distinct() and Values() functions in DAX return non-duplicating distinct values when a column is passed as an argument, there are subtle differences between them:

1. Treatment of Blank Values:

  • Distinct(): Excludes blank values (NULL) from the returned list of distinct values.

  • Values(): Includes blank values in the returned list of distinct values. This can be useful if you want to analyze the distribution of blank values in your data.

2. Argument Types:

  • Distinct(): Accepts column names or any valid table expression as arguments.

  • Values(): Only accepts column names as arguments. You cannot use it with expressions involving multiple columns or calculations.

3. Performance:

  • Distinct(): Generally faster than Values() because it doesn't have to handle blank values.

  • Values(): May be slightly slower than Distinct() due to its need to process blank values. However, the performance difference is usually negligible for most scenarios.

4. Specific Use Cases:

  • Distinct(): Use it when you want to remove duplicates and focus only on unique values without considering blanks.

  • Values(): Use it when you want to include and analyze blank values alongside your distinct values.

Here's a table summarizing the key differences:





Feature

Distinct()

Values()

Blank Values

Excludes

Includes

Argument Types

Column names or expressions

Column names only

Performance

Faster

Slower (slightly)

Use Cases

Unique values without blanks

Distinct values with or without blanks

Remember: When choosing between Distinct() and Values(), consider your specific needs and the presence of blank values in your data. If you're unsure which function to use, try both and compare the results to see which one best suits your analysis.

I hope this clarifies the differences between Distinct() and Values() in DAX! Feel free to ask if you have any further questions about DAX functions or Power BI analysis.


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