[Solved] Identify the mistake in the following self join query:SELECT e1.name, e2.name FROM employees e1 JOIN employees e2 ON e1.manager_id = e2.id WHERE e1.manager_id = NULL; | SQL

SQL - INNER JOIN

Identify the mistake in the following self join query:

SELECT e1.name, e2.name FROM employees e1 JOIN employees e2 ON e1.manager_id = e2.id WHERE e1.manager_id = NULL;

AMissing JOIN condition

BIncorrect table aliasing

CUsing '=' to compare with NULL instead of 'IS NULL'

DUsing JOIN instead of LEFT JOIN

Step-by-Step Solution

Solution:

Step 1: Check WHERE clause
The condition e1.manager_id = NULL is invalid because NULL cannot be compared with '='.
Step 2: Correct NULL comparison
Use IS NULL to check for NULL values in SQL.
Final Answer:
Using '=' to compare with NULL instead of 'IS NULL' -> Option C
Quick Check:
NULL comparisons require IS NULL [OK]

Quick Trick: Use IS NULL to check NULL values [OK]

Common Mistakes:

MISTAKES

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