[Solved] What happens when a correlated subquery is executed in SQL? — Ans: The subquery runs once for each row of the outer query | SQL

SQL - Subqueries

What happens when a correlated subquery is executed in SQL?

AThe subquery runs only once before the outer query

BThe subquery runs independently without referencing the outer query

CThe subquery runs after the outer query completes

DThe subquery runs once for each row of the outer query

Step-by-Step Solution

Solution:

Step 1: Understand correlated subquery execution
A correlated subquery depends on the outer query's current row, so it must run repeatedly for each row.
Step 2: Compare execution models
Unlike a simple subquery that runs once, a correlated subquery executes once per outer row to use that row's data.
Final Answer:
The subquery runs once for each row of the outer query -> Option D
Quick Check:
Correlated subquery execution = runs per outer row [OK]

Quick Trick: Correlated subqueries run repeatedly per outer row [OK]

Common Mistakes:

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What happens when a correlated subquery is executed in SQL?