Which of the following is the correct syntax to perform a self join on a table named employees with alias e1 and e2?

easy📝 Syntax Q12 of 15

SQL - INNER JOIN

Which of the following is the correct syntax to perform a self join on a table named employees with alias e1 and e2?

ASELECT * FROM employees e1 JOIN employees e2 ON e1.id = e2.manager_id;

BSELECT * FROM employees JOIN employees ON id = manager_id;

CSELECT * FROM employees e1, employees e2 ON e1.id = e2.manager_id;

DSELECT * FROM employees e1 INNER JOIN employees e2 ON e1.id = e2.id;

Step-by-Step Solution

Solution:

Step 1: Use table aliases for self join
To join a table to itself, you must use aliases like e1 and e2 to distinguish the two instances.
Step 2: Write the join condition correctly
The join condition should relate columns from the two aliases, for example e1.id = e2.manager_id to find employees and their managers.
Final Answer:
SELECT * FROM employees e1 JOIN employees e2 ON e1.id = e2.manager_id; -> Option A
Quick Check:
Self join syntax = table alias + join condition [OK]

Quick Trick: Always use aliases to distinguish the same table twice [OK]

Common Mistakes:

MISTAKES

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