What does GROUP BY do in SQL?

What does GROUP BY do in SQL?

• A. Sorts rows by a specified column.
• B. Aggregates rows into groups based on specified columns.
• C. Joins rows from two tables.
• D. Filters rows based on a condition.

Answer: (B)

Grouping data in SQL involves collecting rows that share the same values in specified columns into a single group so you can summarize each group. The GROUP BY clause defines how rows are partitioned by listing the columns whose distinct value combinations make up a group. Once grouped, you typically apply aggregate functions like COUNT, SUM, AVG, or MAX to produce one result per group. This is different from sorting (ORDER BY) and filtering (WHERE). Sorting rearranges rows, WHERE filters individual rows before grouping, and to filter after grouping you can use HAVING. For example, grouping by department lets you compute one total salary per department.

Grouping data in SQL involves collecting rows that share the same values in specified columns into a single group so you can summarize each group. The GROUP BY clause defines how rows are partitioned by listing the columns whose distinct value combinations make up a group. Once grouped, you typically apply aggregate functions like COUNT, SUM, AVG, or MAX to produce one result per group. This is different from sorting (ORDER BY) and filtering (WHERE). Sorting rearranges rows, WHERE filters individual rows before grouping, and to filter after grouping you can use HAVING. For example, grouping by department lets you compute one total salary per department.