Add WHERE department IS NOT NULL before GROUP BY.

Use HAVING department IS NOT NULL after GROUP BY.

Replace NULL with a string using COALESCE(department, 'Unknown') in SELECT and GROUP BY.

Solution:Step 1: Understand why no error occursIn standard SQL, GROUP BY handles NULL values correctly by grouping all NULLs together into one group. No error is thrown.Step 2: Confirm no fix neededThe query runs successfully and includes a NULL group in the results.Final Answer:No fix needed; GROUP

[Solved] Consider this query:SELECT department, COUNT(*) FROM employees GROUP BY department;It returns an error. Which fix will correctly handle NULL values in department to avoid errors? | SQL

SQL - GROUP BY and HAVING

Consider this query:

SELECT department, COUNT(*) FROM employees GROUP BY department;

It returns an error. Which fix will correctly handle NULL values in department to avoid errors?

AAdd <code>WHERE department IS NOT NULL</code> before GROUP BY.

BNo fix needed; GROUP BY never errors on NULL.

CUse <code>HAVING department IS NOT NULL</code> after GROUP BY.

DReplace <code>NULL</code> with a string using <code>COALESCE(department, 'Unknown')</code> in SELECT and GROUP BY.

Step-by-Step Solution

Solution:

Step 1: Understand why no error occurs
In standard SQL, GROUP BY handles NULL values correctly by grouping all NULLs together into one group. No error is thrown.
Step 2: Confirm no fix needed
The query runs successfully and includes a NULL group in the results.
Final Answer:
No fix needed; GROUP BY never errors on NULL. -> Option B
Quick Check:
GROUP BY NULL = no error [OK]

Quick Trick: GROUP BY handles NULLs without error [OK]

Common Mistakes:

MISTAKES

Thinking GROUP BY errors on NULLs
Unnecessarily filtering out NULLs with WHERE
Misusing HAVING for pre-group filtering

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Step 1: Understand why no error occurs

Step 2: Confirm no fix needed

Final Answer:

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