[Solved] What is a key characteristic of a correlated subquery in PostgreSQL? — Ans: It runs the inner query once for each row of the outer query. | PostgreSQL

PostgreSQL - Subqueries in PostgreSQL

What is a key characteristic of a correlated subquery in PostgreSQL?

AIt runs the inner query once for each row of the outer query.

BIt runs the inner query only once regardless of outer rows.

CIt always returns a fixed number of rows.

DIt cannot reference columns from the outer query.

Step-by-Step Solution

Solution:

Step 1: Understand the definition of correlated subquery
A correlated subquery references columns from the outer query and runs once per outer row.
Step 2: Compare options with this behavior
Only It runs the inner query once for each row of the outer query. correctly states that the inner query runs once per outer row.
Final Answer:
It runs the inner query once for each row of the outer query. -> Option A
Quick Check:
Correlated subquery = runs per outer row [OK]

Quick Trick: Correlated means inner query depends on outer row [OK]

Common Mistakes:

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What is a key characteristic of a correlated subquery in PostgreSQL?