Which construct groups rows and provides a single value for each group in SQL?

Which construct groups rows and provides a single value for each group in SQL?

• A. AVG
• B. EXTRACT
• C. GROUP BY
• D. HAVING

Answer: (C)

Grouping rows in SQL is accomplished with the GROUP BY clause. It collects rows that share the same values in the specified columns into separate groups. After those groups exist, you typically compute a single value for each group by applying an aggregate function like AVG, SUM, or COUNT in the SELECT list. For example, SELECT department, AVG(salary) AS avg_salary FROM employees GROUP BY department; yields one row per department with the average salary for that department. Remember, AVG alone doesn’t create groups; it reduces rows within the scope you provide. EXTRACT isn’t about grouping, and HAVING filters groups after they’re formed rather than defining the groups themselves.

Grouping rows in SQL is accomplished with the GROUP BY clause. It collects rows that share the same values in the specified columns into separate groups. After those groups exist, you typically compute a single value for each group by applying an aggregate function like AVG, SUM, or COUNT in the SELECT list. For example, SELECT department, AVG(salary) AS avg_salary FROM employees GROUP BY department; yields one row per department with the average salary for that department. Remember, AVG alone doesn’t create groups; it reduces rows within the scope you provide. EXTRACT isn’t about grouping, and HAVING filters groups after they’re formed rather than defining the groups themselves.