[Solved] Why does this query cause an error?SELECT e.name, m.name FROM employees e JOIN employees m ON e.manager_id = m.manager_id; | SQL

SQL - Advanced Joins

Why does this query cause an error?

SELECT e.name, m.name FROM employees e JOIN employees m ON e.manager_id = m.manager_id;

AThe SELECT clause is missing a GROUP BY

BThe table alias 'e' is not defined

CIt joins on manager_id to manager_id, which does not link employee to manager

DThe JOIN keyword is invalid here

Step-by-Step Solution

Solution:

Step 1: Check join condition logic
Joining on e.manager_id = m.manager_id matches employees with the same manager, not employee to manager.
Step 2: Correct join condition needed
To link employee to their manager, join on e.manager_id = m.id.
Final Answer:
It joins on manager_id to manager_id, which does not link employee to manager -> Option C
Quick Check:
Join keys must link employee to manager [OK]

Quick Trick: Join employee.manager_id to manager.id, not manager_id to manager_id [OK]

Common Mistakes:

MISTAKES

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