What is a typical characteristic of aggregate functions in a query?

What is a typical characteristic of aggregate functions in a query?

• A. They always return multiple rows.
• B. They require a GROUP BY for any result.
• C. They often return one row.
• D. They cannot be used with WHERE.

Answer: (C)

Aggregate functions summarize sets of rows into a single value, turning many input rows into one result for each group. When you query without a GROUP BY, the entire result is treated as one group, so you get one row with the aggregate value (for example, the total count or sum across all rows). If you do include a GROUP BY, you still produce one row per group, each containing the aggregate for that specific group. This is why the statement that aggregate functions often return one row is the best fit: their primary behavior is to collapse multiple rows into a single summarized value, either once for the whole result or once per group. The other options don’t fit because they imply a fixed multi-row outcome, require a GROUP BY for any result, or claim they can’t be used with filtering such as WHERE, all of which contradict how aggregation works in SQL.

Aggregate functions summarize sets of rows into a single value, turning many input rows into one result for each group. When you query without a GROUP BY, the entire result is treated as one group, so you get one row with the aggregate value (for example, the total count or sum across all rows). If you do include a GROUP BY, you still produce one row per group, each containing the aggregate for that specific group. This is why the statement that aggregate functions often return one row is the best fit: their primary behavior is to collapse multiple rows into a single summarized value, either once for the whole result or once per group. The other options don’t fit because they imply a fixed multi-row outcome, require a GROUP BY for any result, or claim they can’t be used with filtering such as WHERE, all of which contradict how aggregation works in SQL.