[Solved] Consider this SQL query intended to list employees and their managers:SELECT e.name, m.name AS manager_name FROM employees e JOIN employees m ON e.id = m.manager_id;What is the error in this query? | SQL

SQL - Advanced Joins

Consider this SQL query intended to list employees and their managers:

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

What is the error in this query?

AThe join condition is reversed; it should be e.manager_id = m.id

BThe table alias 'm' is not defined

CThe query should use LEFT JOIN instead of JOIN

DThe SELECT clause should use m.manager_name instead of m.name

Step-by-Step Solution

Solution:

Step 1: Analyze the join condition
The query joins on e.id = m.manager_id, which means employee id equals manager's manager_id, which is incorrect.
Step 2: Correct join condition for manager lookup
To find each employee's manager, join on e.manager_id = m.id so employee's manager_id matches manager's id.
Final Answer:
The join condition is reversed; it should be e.manager_id = m.id -> Option A
Quick Check:
Join on employee.manager_id = manager.id [OK]

Quick Trick: Match child.manager_id to parent.id, not reverse [OK]

Common Mistakes:

MISTAKES

Master "Advanced Joins" in SQL

9 interactive learning modes - each teaches the same concept differently

More SQL Quizzes

Consider this SQL query intended to list employees and their managers: