[Solved] Why does the SUM() function ignore NULL values in a column when calculating the total? — Ans: Because NULL means unknown, so it is excluded from calculations | SQL

SQL - Aggregate Functions

Why does the SUM() function ignore NULL values in a column when calculating the total?

ABecause NULL is treated as zero automatically

BBecause NULL means unknown, so it is excluded from calculations

CBecause SUM() only works on non-nullable columns

DBecause NULL values cause syntax errors in SUM()

Step-by-Step Solution

Solution:

Step 1: Understand NULL meaning
NULL means missing or unknown value, not zero.
Step 2: Behavior of SUM() with NULL
SUM() ignores NULLs to avoid incorrect totals; it sums only known values.
Final Answer:
Because NULL means unknown, so it is excluded from calculations -> Option B
Quick Check:
SUM() skips NULLs, treats as unknown [OK]

Quick Trick: NULL means unknown, so SUM ignores it [OK]

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