What is the difference between a calculated column and a measure in DAX? Calculated columns reference a single row, while measures aggregate across rows. Calculated columns can be used in pivot tables, but measures cannot. Measures require the SuM function, but calculated columns do not. Measures are created in Power BI Desktop, but calculated columns are only in Excel.

1. **Understanding Calculated Columns and Measures** - A **calculated column** is computed for every row in a table. Its value is determined by an expression that works within the context of a single row. Once calculated, these values are stored in the table. - A **measure** is computed on the fly, typically as an aggregation of values across rows. Measures dynamically calculate a result based on the current filter and row context. 2. **Evaluating the Statements** - **Statement:** *"Calculated columns reference a single row, while measures aggregate across rows."* This accurately describes the main difference between the two: calculated columns work at the row level, and measures perform aggregations based on context. - **Other Statements:** - *"Calculated columns can be used in pivot tables, but measures cannot."* This is incorrect because both calculated columns and measures can be used in pivot tables. Measures are often preferred for dynamic aggregation. - *"Measures require the SuM function, but calculated columns do not."* This is misleading. A measure can use any aggregation function (like \( \text{SUM} \), \( \text{AVERAGE} \), etc.), and there is no requirement that it must use the \( \text{SUM} \) function. - *"Measures are created in Power BI Desktop, but calculated columns are only in Excel."* This is false. Both measures and calculated columns are available in Power BI Desktop, and DAX is used in both Excel (via Power Pivot) and Power BI. 3. **Conclusion** The correct and accurate statement is: \[ \text{Calculated columns reference a single row, while measures aggregate across rows.} \] Thus, the main difference is that calculated columns operate row by row, while measures perform aggregations across rows dynamically based on the current context.