Discussion
COUNT(field_name) tallies only those rows that contain a value; it ignores all null values.
Answer: A
Correct answer: True
COUNT(field_name) counts rows in which that field is not null, so nulls reduce the count.
COUNT(*) behaves differently, counting rows regardless of their contents, and the gap between the two is a quick way to find how many nulls a column holds. The same null-skipping applies to SUM, AVG, MIN and MAX, which matters most for AVG: it divides by the number of non-null values, not by the number of rows.
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