[Solved] In a self join, why do we use table aliases like e1 and e2? — Ans: To distinguish between the two instances of the same table | PostgreSQL

PostgreSQL - Joins in PostgreSQL

In a self join, why do we use table aliases like e1 and e2?

ATo distinguish between the two instances of the same table

BTo create new tables automatically

CTo speed up the query execution

DTo avoid using WHERE clause

Step-by-Step Solution

Solution:

Step 1: Recognize table alias purpose
Aliases let us treat the same table as two separate entities in the query.
Step 2: Understand necessity in self join
Without aliases, the database cannot differentiate which instance of the table each column belongs to.
Final Answer:
To distinguish between the two instances of the same table -> Option A
Quick Check:
Aliases in self join = Distinguish tables [OK]

Quick Trick: Use aliases to name table copies in self join [OK]

Common Mistakes:

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In a self join, why do we use table aliases like e1 and e2?