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Why does COUNT(column_name) ignore NULL values internally in SQL?

hard📝 Conceptual Q10 of 15
SQL - Aggregate Functions
Why does COUNT(column_name) ignore NULL values internally in SQL?
ABecause NULL represents unknown or missing data, so it is excluded from counts
BBecause NULL values cause syntax errors in COUNT
CBecause COUNT counts only numeric values
DBecause NULL values are automatically converted to zero
Step-by-Step Solution
Solution:

  1. Step 1: Understand the meaning of NULL in SQL

    NULL means unknown or missing data, not a value.

  2. Step 2: Explain COUNT behavior with NULLs

    COUNT(column_name) excludes NULLs because they do not represent actual data to count.

  3. Final Answer:

    Because NULL represents unknown or missing data, so it is excluded from counts -> Option A

  4. Quick Check:

    NULL means missing data, excluded by COUNT [OK]
Quick Trick: NULL means missing data, so COUNT ignores it [OK]
Common Mistakes:
MISTAKES
  • Thinking NULL causes errors in COUNT
  • Assuming NULL is zero
  • Believing COUNT counts only numbers

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