Final answer:
"Multiple-row functions return one result per group of rows", which is a true statement. These include functions like SUM, which will include all values for calculation, including duplicates, if the DISTINCT keyword is not used.
Step-by-step explanation:
Functions that return one result per group of rows are indeed called multiple-row functions.
This statement is true. Multiple-row functions, also known as group functions, include SUM, AVG, MAX, MIN, and COUNT, and they perform a calculation on a set of values to return a single value representing the group.
When the DISTINCT keyword is not included in the SUM function, the SUM function will include all values in the calculation, including duplicates.
The absence of DISTINCT means that every instance of a value in the dataset will contribute to the total sum. In contrast, using DISTINCT with the SUM function would result in the calculation only considering each unique value once.