alleryStart learning →In a 100-row `employees` table where 20 rows have `salary` NULL,
ACOUNT(*) = 100 and COUNT(salary) = 80
BCOUNT(*) = 80 and COUNT(salary) = 100
CCOUNT(*) = 100 and COUNT(salary) = 100
Dboth return NULL because of the NULL salaries
Answer & Solution
Correct answer: A. COUNT(*) = 100 and COUNT(salary) = 80
COUNT(*) counts rows, regardless of NULL values inside them, so all 100 rows are counted.
COUNT(salary) counts rows where the salary column is NOT NULL
so it skips the 20 NULL-salary rows and returns 80. This pair is a common GATE trap.
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