SQL - GROUP BY and HAVING
Why does SQL treat all NULL values as one group in
GROUP BY even though NULL means 'unknown'?Why does SQL treat all NULL values as one group in GROUP BY even though NULL means 'unknown'?
hard📝 Conceptual Q10 of 15
Step-by-Step Solution
Solution:
Step 1: Understand NULL meaning in SQL
NULL means unknown or missing data, so it cannot be compared as equal.Step 2: Explain grouping behavior
SQL groups all NULLs together to keep those rows in one group for aggregation, avoiding data loss.Final Answer:
Because SQL groups NULLs together to avoid losing data in aggregation. -> Option AQuick Check:
NULLs grouped to keep data, not because they are equal [OK]
Quick Trick: NULL means unknown but grouped together to keep data [OK]
Common Mistakes:
MISTAKES- Thinking NULLs are equal in SQL
- Believing NULLs replaced internally
- Assuming NULLs not allowed in GROUP BY
Master "GROUP BY and HAVING" in SQL
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