[Solved] Find the issue in this query: SELECT AVG(salary) FROM employees WHERE salary != NULL; — Ans: Comparison with NULL using != is invalid, use IS NOT NULL | SQL

SQL - Aggregate Functions

Find the issue in this query: SELECT AVG(salary) FROM employees WHERE salary != NULL;

AMissing GROUP BY clause causes error

BAVG cannot be used with WHERE clause

CComparison with NULL using != is invalid, use IS NOT NULL

DNo issue, query is correct

Step-by-Step Solution

Solution:

Step 1: Understand NULL comparison in WHERE
Comparing with NULL using != or = is invalid; use IS NOT NULL instead.
Step 2: Correct the WHERE clause
Use WHERE salary IS NOT NULL to filter out NULLs properly.
Final Answer:
Comparison with NULL using != is invalid, use IS NOT NULL -> Option C
Quick Check:
Use IS NOT NULL to filter NULLs, not != NULL = A [OK]

Quick Trick: Use IS NOT NULL to check for non-NULL values in WHERE [OK]

Common Mistakes:

MISTAKES

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Find the issue in this query: SELECT AVG(salary) FROM employees WHERE salary != NULL;