Aggregate Functions group by having

Employee(emp_id, dept, salary, bonus)
• salary and bonus may contain NULLs
• dept includes some NULL department rows

Which query filters only departments where more than 3 employees exist?

• WHERE COUNT() > 3

• HAVING COUNT() > 3

• WHERE emp_id > 3

• FILTER COUNT(*) > 3

COUNT(*) vs COUNT(salary) difference?

• COUNT(salary) ignores NULL

• COUNT(*) counts all rows

• Both A and B

• They are always identical

Which returns departments with total bonus > total salary?

• Valid

• Invalid

Which filters employees before grouping?

• WHERE

• HAVING

• GROUP WHERE

• DISTINCT

Evaluate: SELECT dept, SUM(salary) FROM Employee GROUP BY dept HAVING SUM(salary) IS NULL;

• Shows only depts where salary all NULL

• Shows non-NULL salary depts

• Shows error

• Shows all rows

Which counts NULL salary rows per dept?

• Correct

• Wrong

HAVING always needs GROUP BY?

• No

• Yes

Which query shows only departments where avg bonus > 10000?

• HAVING bonus > 10000

• HAVING AVG(bonus) > 10000

• WHERE AVG(bonus) > 10000

• GROUP WHERE AVG(bonus) > 10000

NULL dept values in GROUP BY become:

• A separate NULL group

• Ignored

• Merged into highest dept value

• Returns error

Which is most accurate?

• HAVING filters aggregated results

• HAVING works same as WHERE

• HAVING never uses aggregate functions

• HAVING comes before GROUP BY