What does GROUP BY do in a query?

What does GROUP BY do in a query?

• A. Aggregates all rows into a single result row
• B. Sorts rows in a particular order
• C. Filters rows based on a condition
• D. Groups records by common characteristics to produce subtotals

Answer: (D)

Grouping by a set of columns combines rows that share the same values in those columns, and then you typically apply aggregates to produce one result per group, i.e., subtotals for each group. This is why it yields multiple lines—one for each distinct combination of the grouping columns—rather than a single row. It’s not about sorting (that’s ORDER BY) or filtering (that’s WHERE). For example, selecting department and total salary with GROUP BY department returns one row per department with the sum of salaries for that department.

Grouping by a set of columns combines rows that share the same values in those columns, and then you typically apply aggregates to produce one result per group, i.e., subtotals for each group. This is why it yields multiple lines—one for each distinct combination of the grouping columns—rather than a single row. It’s not about sorting (that’s ORDER BY) or filtering (that’s WHERE). For example, selecting department and total salary with GROUP BY department returns one row per department with the sum of salaries for that department.