Does AVG count the missing row?

Question

Accepted Answer

AVG ignores NULL values entirely - it divides the sum of non-NULL values by the count of non-NULL values. Here it computes (1 + 2) / 2 = 1.5, not (1 + 2 + 0) / 3 = 1.0. This behavior is consistent across all aggregate functions: SUM, COUNT(col), MIN, and MAX all skip NULLs. If you want NULL to count as zero, use AVG(COALESCE(score, 0)) instead.

id	score
1	1
2	2
3	NULL