SUMX and iterators in Power BI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the SUMX function do in Power BI?

SUMX goes row by row over a table, calculates an expression for each row, then adds all those results together.

beginner

Why do we call SUMX an iterator function?

Because it looks at each row one by one and performs a calculation before summing up the results.

beginner

Write a simple example of SUMX to calculate total sales where each row has Quantity and Price.

Total Sales = SUMX(Sales, Sales[Quantity] * Sales[Price])

intermediate

What is the difference between SUM and SUMX?

SUM adds values in one column directly. SUMX calculates an expression for each row first, then adds those results.

intermediate

Can SUMX be used with any table or only with the original data table?

SUMX can be used with any table or table expression, including filtered or calculated tables.

What does SUMX do?

A Calculates an expression for each row and sums the results

B Filters rows based on a condition

C Adds all values in a single column directly

D Creates a new table from existing data

SUMX iterates row by row, calculates an expression, then sums those results.

Which of these is a correct use of SUMX?

A SUMX(Sales, Sales[Quantity])

B SUMX(Sales, Sales[Price] + 10)

C SUMX(Sales[Quantity])

D SUMX(Sales, Sales[Quantity] * Sales[Price])

Option D calculates total sales by multiplying quantity and price for each row, then sums.

What type of function is SUMX?

A Iterator function

B Aggregation function

C Filter function

D Logical function

SUMX is an iterator because it processes each row individually.

Which is true about SUMX compared to SUM?

A SUMX is faster than SUM

B SUMX can calculate expressions per row, SUM cannot

C SUMX only works on numeric columns

D SUMX does not support filters

SUMX calculates expressions row by row, while SUM just adds column values.

Can SUMX be used on a filtered table?

A Only if the table has less than 1000 rows

B No, only on full tables

C Yes, it works on any table or table expression

D Only if the table has numeric columns

SUMX works on any table or table expression, including filtered tables.

Explain in your own words how SUMX works and why it is called an iterator.

Think about how you would add up prices times quantities for each item in a shopping list.

Describe a real-life example where using SUMX is better than using SUM.

Imagine you want total money made from selling different products with different prices and quantities.